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dockerでBASIC:docker(116)
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Last updated at Posted at 2021-05-05
dockerでBASICを使おうとGCCで起動
$ docker run -it gcc /bin/bash
basicを検索
# apt update; apt -y upgrade; apt install man
# apt search basic
Sorting... Done
Full Text Search... Done
acheck-rules/stable 0.3.3 all
Basic rules for acheck
bwbasic/stable 2.20pl2-11+b2 amd64
Bywater BASIC Interpreter
yabasic/stable 1:2.82.0-1 amd64
Yet Another BASIC interpreter
# apt install yabasic
# man yabasic
yabasic(1) General Commands Manual yabasic(1)
NAME
yabasic - yet another Basic
SYNOPSIS
yabasic [OPTIONS] [FILENAME [ARGUMENTS]]
DESCRIPTION
Yabasic implements the most common and simple elements of the basic lan-
guage. It comes with goto/gosub, with various loops, with user defined
subroutines and libraries. Yabasic does simple graphics and printing.
Yabasic runs under Unix and Windows, it is small, open source and free.
This man-page is derived from yabasic.htm, which too should be installed
on your system; per default in
/usr/local/share/applications/yabasic/yabasic.htm.
The same information can also be found on www.yabasic.de
Here is its content:
Yabasic
----------------------------------------------------------------------------
---
Table of Contents
1. Introduction
About this document
About yabasic
2. The yabasic-program under Windows
Starting yabasic
Options
The context Menu
3. The yabasic-program under Unix
Starting yabasic
Options
Setting defaults
4. Command line options of yabasic
5. Some features of yabasic, explained by topic
print, input and others
Control statements: loops, if and switch
Drawing and painting
Reading from and writing to files
Subroutines and Libraries
String processing
Arithmetic and numbers
Data and such
Other interesting commands.
6. All commands and functions of yabasic listed by topic
Number processing and conversion
Conditions and control structures
Data keeping and processing
String processing
File operations and printing
Subroutines and libraries
Other commands
Graphics and printing
7. All commands and functions of yabasic grouped alphabetically
A
B
C
D
E
F
G
H
I
L
M
N
O
P
R
S
T
U
V
W
X
Special characters
Reserved Words
8. Some general concepts and terms
Logical shortcuts
Conditions and expressions
References on arrays
Specifying Filenames under Windows
Escape-sequences
Creating a standalone program from your yabasic-program
9. A few example programs
A very simple program
The demo of yabasic
10. The Copyright of yabasic
Chapter 1. Introduction
About this document
About yabasic
About this document
This document describes yabasic. You will find information about the yabasic
interpreter (the program yabasic under Unix or yabasic.exe under Windows) as
well as the language (which is, of course, a sort of basic) itself.
This document applies to version 2.82 of yabasic
However, this document does not contain the latest news about yabasic or a F
AQ.
As such information tends to change rapidly, it is presented online only at
www.yabasic.de.
Although basic has its reputation as a language for beginning programmers, t
his
is not an introduction to programming at large. Rather this text assumes, th
at
the reader has some (moderate) experience with writing and starting computer
programs.
About yabasic
yabasic is a traditional basic interpreter. It understands most of the typic
al
basic-constructs, like goto, gosub, line numbers, read, data or
string-variables with a trailing '$'. But on the other hand, yabasic impleme
nts
some more advanced programming-constructs like subroutines or libraries (but
not objects). yabasic works much the same under Unix and Windows.
yabasic puts emphasis on giving results quickly and easily; therefore simple
commands are provided to open a graphic window, print the graphics or contro
l
the console screen and get keyboard or mouse information. The example below
opens a window, draws a circle and prints the graphic:
open window 100,100
open printer
circle 50,50,40
text 10,50,"Press any key to get a printout"
clear screen
inkey$
close printer
close window
This example has fewer lines, than it would have in many other programming
languages. In the end however yabasic lacks behind more advanced and modern
programming languages like C++ or Java. But as far as it goes it tends to gi
ve
you results more quickly and easily.
Chapter 2. The yabasic-program under Windows
Starting yabasic
Options
The context Menu
Starting yabasic
Once, yabasic has been set up correctly, there are three ways to start it:
1. Right click on your desktop: The desktop menu appears with a submenu nam
ed
new. From this submenu choose yabasic. This will create a new icon on yo
ur
desktop. If you right click on this icon, its context menu will appear;
choose Execute to execute the program.
2. As a variant of the way described above, you may simply create a file wi
th
the ending .yab (e.g. with your favorite editor). Everything else then
works as described above.
3. From the start-menu: Choose yabasic from your start-menu. A console-wind
ow
will open and you will be asked to type in your program. Once you are
finished, you need to type return twice, and yabasic will parse and exec
ute
your program.
Note
This is not the preferred way of starting yabasic ! Simply because the
program, that you have typed, can not be saved and will be lost inevitab
ly
! There is no such thing as a save-command and therefore no way to conse
rve
the program, that you have typed. This mode is only intended for quick
hacks, and short programs.
Options
Under Windows yabasic will mostly be invoked by double-clicking on an
appropriate icon; this way you do not have a chance to specify any of the
command line options below. However, advanced users may change the librarypa
th
in the registry, which has the same effect as specifying it as an option on
the
command line.
See the chapter on options for a complete list of all options, either on Uni
x
or Windows.
The context Menu
Like every other icon under Windows, the icon of every yabasic-program has a
context menu offering the most frequent operations, that may be applied to a
yabasic-program.
Execute
This will invoke yabasic to execute your program. The same happens, if y
ou
double click on the icon.
Edit
notepad will be invoked, allowing you to edit your program.
View docu
This will present the embedded documentation of your program. Embedded
documentation is created with the special comment doc.
Chapter 3. The yabasic-program under Unix
Starting yabasic
Options
Setting defaults
Starting yabasic
If your system administrator (vulgo root) has installed yabasic correctly,
there are three ways to start it:
1. You may use your favorite editor (emacs, vi ?) to put your program into
a
file (e.g. foo). Make sure that the very first line starts with the
characters '#!' followed by the full pathname of yabasic (e.g. '#!/usr/
local/bin/yabasic'). This she-bang-line ensures, that your Unix will inv
oke
yabasic to execute your program (see also the entry for the hash
-character). Moreover, you will need to change the permissions of your
yabasic-program foo, e.g. chmod u+x foo. After that you may invoke yabas
ic
to invoke your program by simply typing foo (without even mentioning
yabasic). However, if your PATH-variable does not contain a single dot
('.') you will have to type the full pathname of your program: e.g. /hom
e/
ihm/foo (or at least ./foo).
2. Save your program into a file (e.g. foo) and type yabasic foo. This
assumes, that the directory, where yabasic resides, is contained within
your PATH-variable.
3. Finally your may simply type yabasic (maybe it will be necessary to incl
ude
its full pathname). This will make yabasic come up and you will be asked
to
type in your program. Once you are finished, you need to type return twi
ce,
and yabasic will parse and execute your program.
Note
This is not the preferred way of starting yabasic ! Simply because the
program, that you have typed, can not be saved and will be lost inevitab
ly
! There is no such thing as a save-command and therefore no way to conse
rve
the program, that you have typed. This mode is only intended for quick
hacks, and short programs, i.e. for using yabasic as some sort of fancy
desktop calculator.
Options
yabasic accepts a number of options on the command line.
See chapter on options for a complete list of all options, either on Unix or
Windows.
Setting defaults
If you want to set some options once for all, you may put them into your
X-Windows resource file. This is usually the file .Xresources or some such
within your home directory (type man X for details).
Here is a sample section, which may appear within this file:
yabasic*foreground: blue
yabasic*background: gold
yabasic*geometry: +10+10
yabasic*font: 9x15
This will set the foreground color of the graphic-window to blue and the
background color to gold. The window will appear at position 10,10 and the text
font will be 9x15.
Chapter 4. Command line options of yabasic
Here are the options, that yabasic accepts on the command line (both under Unix
and Windows).
All the options below may be abbreviated (and one hyphen may be dropped), as
long as the abbreviation does not become ambiguous. For example, you may write
-e instead of --execute.
--help or -?
Prints a short help message, which itself describes two further
help-options.
--version
Prints the version of yabasic.
--infolevel INFOLEVEL
Change the infolevel of yabasic, where INFOLEVEL can be one of debug, note,
warning, error, fatal and bison (the default is warning). This option
changes the amount of debugging-information yabasic produces. However,
normally only the author of yabasic (me !) would want to change this.
--execute A-PROGRAM-AS-A-SINGLE-STRING
With this option you may specify some yabasic-code to be executed right
away. This is useful for very short programs, which you do not want to save
to a file. If this option is given, yabasic will not read any code from a
file. E.g.
yabasic -e 'for a=1 to 10:print a*a:next a'
prints the square numbers from 1 to 10.
--bind NAME-OF-STANDALONE-PROGRAM
Create a standalone program (whose name is specified by
NAME-OF-STANDALONE-PROGRAM) from the yabasic-program, that is specified on
the command line. See the section about creating a standalone-program for
details.
--geometry +X-POSITION+Y-POSITION
Sets the position of the graphic window, that is opened by open window (the
size of this window, of course, is specified within the open
window-command). An example would be -geometry +20+10, which would place
the graphic window 10 pixels below the upper border and 20 pixels right of
the left border of the screen. This value cannot be changed, once yabasic
has been started.
-fg FOREGROUND-COLOR or --foreground FOREGROUND-COLOR
Unix only. Define the foreground color for the graphics-window (that will
be opened with open window). The usual X11 color names, like red, green,?
are accepted. This value cannot be changed, once yabasic has been started.
-bg BACKGROUND-COLOR or --background BACKGROUND-COLOR
Unix only. Define the background color for the graphics-window. The usual
X11 color names are accepted. This value cannot be changed, once yabasic
has been started.
--display X11-DISPLAY-SPECIFICATION
Unix only. Specify the display, where the graphics window of yabasic should
appear. Normally this value will be already present within the environment
variable DISPLAY.
--font NAME-OF-FONT
Under Unix. Name of the font, which will be used for text within the
graphics window.
--font NAME-OF-FONT
Under Windows. Name of the font, which will be used for graphic-text; can
be any of decorative, dontcare, modern, roman, script, swiss. You may
append a fontsize (measured in pixels) to any of those fontnames; for
example -font swiss30 chooses a swiss-type font with a size of 30 pixels
.
--docu NAME-OF-A-PROGRAM
Print the embedded documentation of the named program. The embedded
documentation of a program consists of all the comments within the program,
which start with the special keyword doc. This documentation can also be
seen by choosing the corresponding entry from the context-menu of any
yabasic-program.
--check
Check for possible compatibility problems within your yabasic-program. E
.g.
this option reports, if you are using a function, that has recently
changed.
--librarypath DIRECTORY-WITH-LIBRARIES
Change the directory, wherein libraries will be searched and imported (with
the import-command). See also import for more information about the way,
libraries are searched.
--
Do not try to parse any further options; rather pass the subsequent words
from the commandline to yabasic.
Chapter 5. Some features of yabasic, explained by topic
print, input and others
Control statements: loops, if and switch
Drawing and painting
Reading from and writing to files
Subroutines and Libraries
String processing
Arithmetic and numbers
Data and such
Other interesting commands.
This chapter has sections for some of the major features of yabasic and names a
few commands related with each area. So, depending on your interest, you find
the most important commands of this area named; the other commands from this
area may then be discovered through the links in the see also-section.
print, input and others
The print-command is used to put text on the text screen. Here, the term text
screen stands for your terminal (under Unix) or the console window (under
Windows).
At the bottom line, print simply outputs its argument to the text window.
However, once you have called clear screen you may use advanced features like
printing colors or copying areas of text with getscreen$ or putscreen.
You may ask the user for input with the input-command; use inkey$ to get each
key as soon as it is pressed.
Control statements: loops, if and switch
Of course, yabasic has the goto- and gosub-statements; you may go to a label or
a line number (which is just a special kind of label). goto, despite its bad
reputation ([goto considered harmful]), has still its good uses; however in
many cases you are probably better off with loops like repeat-until, while-wend
or do-loop; you may leave any of these loops with the break-statement or start
the next iteration immediately with continue.
Decisions can be made with the if-statement, which comes either in a short and
a long form. The short form has no then-keyword and extends up to the end of
the line. The long form extends up to the final endif and may use some of the
keywords then (which introduces the long form), else or elsif.
If you want to test the result of an expression against many different values,
you should probably use the switch-statement.
Drawing and painting
You need to call open window before you may draw anything with either line,
circle, rectangle or triangle; all of these statements may be decorated with
clear or fill. If you want to change the colour for drawing, use colour. Note
however, that there can only be a single window open at any given moment in
time.
Everything you have drawn can be send to your printer too, if you use the open
printer command.
To allow for some (very) limited version of animated graphics, yabasic offers
the commands getbit$ and putbit, which retrieve rectangular regions from the
graphics-window into a string or vice versa.
If you want to sense mouse-clicks, you may use the inkey$-function.
Reading from and writing to files
Before you may read or write a file, you need to open it; once you are done,
you should close it. Each open file is designated by a simple number, which
might be stored within a variable and must be supplied if you want to access
the file. This is simply done by putting a hash ('#') followed by the number of
the file after the keyword input (for reading from) or print (for writing to a
file) respectively.
If you need more control, you may consider reading and writing one byte at a
time, using the multi-purpose commands peek and poke.
Subroutines and Libraries
The best way to break any yabasic-program into smaller, more manageable chunks
are subroutines and libraries. They are yabasic's most advanced means of
structuring a program.
Subroutines are created with the command sub. they accept parameters and may
return a value. Subroutines can be called much like any builtin function of
yabasic; therefore they allow one to extend the language itself.
Once you have created a set of related subroutines and you feel that they could
be useful in other programs too, you may collect them into a library. Such a
library is contained within a separate file and may be included in any of your
programs, using the keyword import, which see.
String processing
yabasic has a set of functions to extract parts from a string: left$, mid$ and
right$. Note, that all of them can be assigned to, i.e. they may change part of
a string.
If you want to split a string into tokens you should use the functions token
or
split.
Some functions are handy for normalizing a string: upper$ and lower$ convert
a
string to all upper or lower case respectively, whereas chomp$ cuts of any
trailing newline character, but only if present.
chr$ and str$ convert a string into a number, both in different ways.
To analyze a string use instr (finding one string within the other) or glob
(testing a string against a simple pattern).
To concatenate strings use the operator + like in a$ + b$.
You may also see the complete list of a string processing functions.
Arithmetic and numbers
Yabasic handles numbers and arithmetic: You may calculate trigonometric
functions like sin or atan, or logarithms (with log). Bitwise operations, li
ke
and or or are available as well min or max (calculate the minimum or maximum
of
its argument) or mod or int (reminder of a division or integer part or a
number).
Conversion between numerical bases can be done with hex$ and dec. And you ma
y
write hexadecimal constants in the usual way, e.g.
print 0xff
. All calculations in yabasic are done with double precision.
Data and such
You may store data within your program within data-statements; during execut
ion
you will probably want to read it into arrays, which must have been dimed
before.
Other interesting commands.
* Yabasic programs may start other programs with the commands system and
system$.
* peek and poke allow one to get and set internal information; either for
the
operating system (i.e. Unix or Windows) or yabasic itself.
* The current time or date can be retrieved with (guess what !) time$ and
date$.
Chapter 6. All commands and functions of yabasic listed by topic
Number processing and conversion
Conditions and control structures
Data keeping and processing
String processing
File operations and printing
Subroutines and libraries
Other commands
Graphics and printing
Number processing and conversion
abs()
returns the absolute value of its numeric argument
acos()
returns the arcus cosine of its numeric argument
and()
the bitwise arithmetic and
asin()
returns the arcus sine of its numeric argument
atan()
returns the arctangent of its numeric argument
bin$()
converts a number into a sequence of binary digits
cos()
return the cosine of its single argument
dec()
convert a base 2 or base 16 number into decimal form
eor()
compute the bitwise exclusive or of its two arguments
euler
another name for the constant 2.71828182864
exp()
compute the exponential function of its single argument
frac()
return the fractional part of its numeric argument
int()
return the integer part of its single numeric argument
ceil()
return the smallest integral number, that is greater or equal than i
ts
argument
floor()
return the largest integral number, that is smaller or equal than it
s
argument
log()
compute the natural logarithm
max()
return the larger of its two arguments
min()
return the smaller of its two arguments
mod
compute the remainder of a division
or()
arithmetic or, used for bit-operations
pi
a constant with the value 3.14159
ran()
return a random number
sig()
return the sign of its argument
sin()
return the sine of its single argument
sqr()
compute the square of its argument
sqrt()
compute the square root of its argument
tan()
return the tangent of its argument
xor()
compute the exclusive or
** or ^
raise its first argument to the power of its second
Conditions and control structures
and
logical and, used in conditions
break
breaks out of a switch statement or a loop
case
mark the different cases within a switch-statement
continue
start the next iteration of a for-, do-, repeat- or while-loop
default
mark the default-branch within a switch-statement
do
start a (conditionless) do-loop
else
mark an alternative within an if-statement
elsif
starts an alternate condition within an if-statement
end
terminate your program
endif
ends an if-statement
false
a constant with the value of 0
fi
another name for endif
for
starts a for-loop
gosub
continue execution at another point within your program (and return
later)
goto
continue execution at another point within your program (and never c
ome
back)
if
evaluate a condition and execute statements or not, depending on the
result
label
mark a specific location within your program for goto, gosub or rest
ore
loop
marks the end of an infinite loop
next
mark the end of a for loop
not
negate an expression; can be written as !
on gosub
jump to one of multiple gosub-targets
on goto
jump to one of many goto-targets
on interrupt
change reaction on keyboard interrupts
logical or
logical or, used in conditions
pause
pause, sleep, wait for the specified number of seconds
repeat
start a repeat-loop
return
return from a subroutine or a gosub
sleep
pause, sleep, wait for the specified number of seconds
switch
select one of many alternatives depending on a value
then
tell the long from the short form of the if-statement
true
a constant with the value of 1
until
end a repeat-loop
wait
pause, sleep, wait for the specified number of seconds
wend
end a while-loop
while
start a while-loop
:
separate commands from each other
Data keeping and processing
arraydim()
returns the dimension of the array, which is passed as an array refe
rence
arraysize()
returns the size of a dimension of an array
data
introduces a list of data-items
dim
create an array prior to its first use
read
read data from data-statements
redim
create an array prior to its first use. A synonym for dim
restore
reposition the data-pointer
String processing
asc()
accepts a string and returns the position of its first character wit
hin the
ascii charset
chomp$()
Chop of the trailing newline of its string-argument; if the string d
oes not
end in a newline, the string is returned unchanged
chr$()
accepts a number and returns the character at this position within t
he
ascii charset
glob()
check if a string matches a simple pattern
hex$()
convert a number into hexadecimal
instr()
searches its second argument within the first; returns its position
if
found
left$()
return (or change) left end of a string
len()
return the length of a string
lower$()
convert a string to lower case
ltrim$()
trim spaces at the left end of a string
mid$()
return (or change) characters from within a string
right$()
return (or change) the right end of a string
split()
split a string into many strings
str$()
convert a number into a string
token()
split a string into multiple strings
trim$()
remove leading and trailing spaces from its argument
upper$()
convert a string to upper case
val()
converts a string to a number
File operations and printing
at()
can be used in the print-command to place the output at a specified
position
beep
ring the bell within your computer; a synonym for bell
bell
ring the bell within your computer (just as beep)
clear screen
erases the text window
close
close a file, which has been opened before
close printer
stops printing of graphics
print color
print with color
print colour
see print color
eof
check, if an open file contains data
getscreen$()
returns a string representing a rectangular section of the text term
inal
inkey$
wait, until a key is pressed
input
read input from the user (or from a file) and assign it to a variabl
e
line input
read in a whole line of text and assign it to a variable
open
open a file
open printer
open printer for printing graphics
print
Write to terminal or file
putscreen
draw a rectangle of characters into the text terminal
reverse
print reverse (background and foreground colors exchanged)
screen
as clear screen clears the text window
seek()
change the position within an open file
tell
get the current position within an open file
using
Specify the format for printing a number
#
either a comment or a marker for a file-number
@
synonymous to at
;
suppress the implicit newline after a print-statement
Subroutines and libraries
end sub
ends a subroutine definition
export
mark a function as globally visible
import
import a library
local
mark a variable as local to a subroutine
numparams
return the number of parameters, that have been passed to a subrouti
ne
return
return from a subroutine or a gosub
static
preserves the value of a variable between calls to a subroutine
step
specifies the increment step in a for-loop
sub
declare a user defined subroutine
Other commands
bind()
Binds a yabasic-program and the yabasic-interpreter together into a
standalone program.
compile
compile a string with yabasic-code on the fly
date$
returns a string with various components of the current date
doc
special comment, which might be retrieved by the program itself
docu$
special array, containing the contents of all docu-statement within
the
program
error
raise an error and terminate your program
execute$()
execute a user defined subroutine, which must return a string
execute()
execute a user defined subroutine, which must return a number
exit
terminate your program
pause
pause, sleep, wait for the specified number of seconds
peek
retrieve various internal information
peek$
retrieve various internal string-information
poke
change selected internals of yabasic
rem
start a comment
sleep
pause, sleep, wait for the specified number of seconds
system()
hand a statement over to your operating system and return its exitco
de
system$()
hand a statement over to your operating system and return its output
time$
return a string containing the current time
to
this keyword appears as part of other statements
wait
pause, sleep, wait for the specified number of seconds
//
starts a comment
:
separate commands from each other
Graphics and printing
backcolor
specify the colour for subsequent drawing of the background
box
draw a rectangle. A synonym for rectangle
circle
draws a circle in the graphic-window
clear
Erase circles, rectangles or triangless
clear window
clear the graphic window and begin a new page, if printing is under
way
close curve
close a curve, that has been drawn by the line-command
close window
close the graphics-window
colour
specify the colour for subsequent drawing
dot
draw a dot in the graphic-window
fill
draw a filled circles, rectangles or triangles
getbit$()
return a string representing the bit pattern of a rectangle within t
he
graphic window
line
draw a line
mouseb
extract the state of the mousebuttons from a string returned by inke
y$
mousemod
return the state of the modifier keys during a mouseclick
mousex
return the x-position of a mouseclick
mousey
return the y-position of a mouseclick
new curve
start a new curve, that will be drawn with the line-command
open window
open a graphic window
putbit
draw a rectangle of pixels into the graphic window
rectangle
draw a rectangle
triangle
draw a triangle
text
write text into your graphic-window
window origin
move the origin of a window
Chapter 7. All commands and functions of yabasic grouped alphabetically
A
B
C
D
E
F
G
H
I
L
M
N
O
P
R
S
T
U
V
W
X
Special characters
Reserved Words
A
abs() ? returns the absolute value of its numeric argument
acos() ? returns the arcus cosine of its numeric argument
and ? logical and, used in conditions
and() ? the bitwise arithmetic and
arraydim() ? returns the dimension of the array, which is passed as an a
rray
reference
arraysize() ? returns the size of a dimension of an array
asc() ? accepts a string and returns the position of its first character
within
the ascii charset
asin() ? returns the arcus sine of its numeric argument
at() ? can be used in the print-command to place the output at a specifi
ed
position
atan() ? returns the arctangent of its numeric argument
Name
abs() ? returns the absolute value of its numeric argument
Synopsis
y=abs(x)
Description
If the argument of the abs-function is positive (e.g. 2) it is returned
unchanged, if the argument is negative (e.g. -1) it is returned as a pos
itive
value (e.g. 1).
Example
print abs(-2),abs(2)
This example will print 2 2
See also
sig
------------------------------------------------------------------------
-------
Name
acos() ? returns the arcus cosine of its numeric argument
Synopsis
x=acos(angle)
Description
acos is the arcus cosine-function, i.e. the inverse of the cos-function.
Or,
more elaborate: It Returns the angle (in radians, not degrees !), which,
fed to
the cosine-function will produce the argument passed to the acos-functio
n.
Example
print acos(0.5),acos(cos(pi))
This example will print 1.0472 3.14159 which are ?/3 and ? respectively.
See also
cos, asin
------------------------------------------------------------------------
-------
Name
and ? logical and, used in conditions
Synopsis
if (a and b) ?
while (a and b) ?
Description
Used in conditions (e.g within if, while or until) to join two expressio
ns.
Returns true, if and only if its left and right argument are both true a
nd
false otherwise.
Note, that logical shortcuts may take place.
Example
input "Please enter a number" a
if (a>=1 and a<=9) print "your input is between 1 and 9"
See also
or,not
------------------------------------------------------------------------
-------
Name
and() ? the bitwise arithmetic and
Synopsis
x=and(a,b)
Description
Used to compute the bitwise and of both its argument. Both arguments are
treated as binary numbers (i.e. a series of 0 and 1); a bit of the resul
ting
value will then be 1, if both arguments have a 1 at this position in the
ir
binary representation.
Note, that both arguments are silently converted to integer values and t
hat
negative numbers have their own binary representation and may lead to
unexpected results when passed to and.
Example
print and(6,3)
This will print 2. This result is clear, if you note, that the binary
representation of 6 and 3 are 110 and 011 respectively; this will yield
010 in
binary representation or 2 as decimal.
See also
or, eor and not
------------------------------------------------------------------------
-------
Name
arraydim() ? returns the dimension of the array, which is passed as an a
rray
reference
Synopsis
a=arraydim(b())
Description
If you apply the arraydim()-function on a one-dimensional array (i.e. a
vector)
it will return 1, on a two-dimensional array (i.e. a matrix) it will ret
urn 2,
and so on.
This is mostly used within subroutines, which expect an array among thei
r
parameters. Such subroutines tend to use the arraydim-function to check,
if the
array which has been passed, has the right dimension. E.g. a subroutine
to
multiply two matrices may want to check, if it really is invoked with tw
o
2-dimensional arrays.
Example
dim a(10,10),b(10)
print arraydim(a()),arraydim(b())
This will print 2 1, which are the dimension of the arrays a() and b().
You may
check out the function arraysize for a full-fledged example.
See also
arraysize and dim.
------------------------------------------------------------------------
-------
Name
arraysize() ? returns the size of a dimension of an array
Synopsis
x=arraysize(a(),b)
Description
The arraysize-function computes the size of a specified dimension of a
specified array. Here, size stands for the maximum number, that may be u
sed as
an index for this array. The first argument to this function must be an
reference to an array, the second one specifies, which of the multiple
dimensions of the array should be taken to calculate the size.
An Example involving subroutines: Let's say, an array has been declared
as dim
a(10,20) (that is a two-dimensional array or a matrix). If this array is
passed
as an array reference to a subroutine, this sub will not know, what sort
of
array has been passed. With the arraydim-function the sub will be able t
o find
the dimension of the array, with the arraysize-function it will be able
to find
out the size of this array in its two dimensions, which will be 10 and 2
0
respectively.
Our sample array is two dimensional; if you envision it as a matrix this
matrix
has 10 lines and 20 columns (see the dim-statement above. To state it mo
re
formally: The first dimension (lines) has a size of 10, the second dimen
sion
(columns) has a size of 20; these numbers are those returned by arraysiz
e(a
(),1) and arraysize(a(),2) respectively. Refer to the example below for
a
typical usage.
Example
rem
rem This program adds two matrices elementwise.
rem
dim a(10,20),b(10,20),c(10,20)
rem initialization of the arrays a() and b()
for y=1 to 10:for x=1 to 20
a(y,x)=int(ran(4)):b(y,x)=int(ran(4))
next x:next y
matadd(a(),b(),c())
print "Result:"
for x=1 to 20
for y=10 to 1 step -1
print c(y,x)," ";
next y
print
next x
sub matadd(m1(),m2(),r())
rem This sub will add the matrices m1() and m2()
rem elementwise and store the result within r()
rem This is not very useful but easy to implement.
rem However, this sub excels in checking its arguments
rem with arraydim() and arraysize()
local x:local y
if (arraydim(m1())<>2 or arraydim(m2())<>2 or arraydim(r())<>2) then
error "Need two dimensional arrays as input"
endif
y=arraysize(m1(),1):x=arraysize(m1(),2)
if (arraysize(m2(),1)<>y or arraysize(m2(),2)<>x) then
error "The two matrices cannot be added elementwise"
endif
if (arraysize(r(),1)<>y or arraysize(r(),2)<>x) then
error "The result cannot be stored in the third argument"
endif
local xx:local yy
for xx=1 to x
for yy=1 to y
r(yy,xx)=m1(yy,xx)+m2(yy,xx)
next yy
next xx
end sub
See also
arraydim and dim.
------------------------------------------------------------------------
-------
Name
asc() ? accepts a string and returns the position of its first character
within
the ascii charset
Synopsis
a=asc(char$)
Description
The asc-function accepts a string, takes its first character and looks i
t up
within the ascii-charset; this position will be returned. The asc-functi
on is
the opposite of the chr$-function. There are valid uses for asc, however
,
comparing strings (i.e. to bring them into alphabetical sequence) is not
among
them; in such many cases you might consider to compare strings directly
with <,
= and > (rather than converting a string to a number and comparing this
number).
Example
input "Please enter a letter between 'a' and 'y': " a$
if (a$<"a" or a$>"y") print a$," is not in the proper range":end
print "The letter after ",a$," is ",chr$(asc(a$)+1)
See also
chr$
------------------------------------------------------------------------
-------
Name
asin() ? returns the arcus sine of its numeric argument
Synopsis
angle=asin(x)
Description
acos is the arcus sine-function, i.e. the inverse of the sin-function. O
r, more
elaborate: It Returns the angle (in radians, not degrees !), which, fed
to the
sine-function will produce the argument passed to the asin-function.
Example
print asin(0.5),asin(sin(pi))
This will print 0.523599 -2.06823e-13 which is ? and almost 0 respective
ly.
See also
sin, acos
------------------------------------------------------------------------
-------
Name
at() ? can be used in the print-command to place the output at a specifi
ed
position
Synopsis
clear screen
?
print at(a,b)
print @(a,b)
Description
The at-clause takes two numeric arguments (e.g. at(2,3)) and can be inse
rted
after the print-keyword. at() can be used only if clear screen has been
executed at least once within the program (otherwise you will get an err
or).
The two numeric arguments of the at-function may range from 0 to the wid
th of
your terminal minus 1, and from 0 to the height of your terminal minus 1
; if
any argument exceeds these values, it will be truncated accordingly. How
ever,
yabasic has no influence on the size of your terminal (80x25 is a common
, but
not mandatory), the size of your terminal and the maximum values accepta
ble
within the at-clause may vary. To get the size of your terminal you may
use the
peek-function: peek("screenwidth") returns the width of your terminal an
d peek
("screenheight") its height.
Example
clear screen
maxx=peek("screenwidth")-1:maxy=peek("screenheight")-1
for x=0 to maxx
print at(x,maxy*(0.5+sin(2*pi*x/maxx)/2)) "*"
next x
This example plots a full period of the sine-function across the screen.
See also
print, clear screen, color
------------------------------------------------------------------------
-------
Name
atan() ? returns the arctangent of its numeric argument
Synopsis
angle=atan(a,b)
angle=atan(a)
Description
atan is the arctangent-function, i.e. the inverse of the tan-function. O
r, more
elaborate: It Returns the angle (in radians, not degrees !), which, fed
to the
tan-function will produce the argument passed to the atan-function.
The atan-function has a second form, which accepts two arguments: atan(a
,b)
which is (mostly) equivalent to atan(a/b) except for the fact, that the
two-argument-form returns an angle in the range -? to ?, whereas the
one-argument-form returns an angle in the range -?/2 to ?/2. To understa
nd this
you have to be good at math.
Example
print atan(1),atan(tan(pi)),atan(-0,-1),atan(-0,1)
This will print 0.463648 2.06823e-13 -3.14159 3.14159 which is ?/4, almo
st 0,
-? and ? respectively.
See also
tan, sin
B
backcolor ? change color for background of graphic window
backcolour ? see backcolor
beep ? ring the bell within your computer; a synonym for bell
bell ? ring the bell within your computer (just as beep)
bin$() ? converts a number into a sequence of binary digits
bind() ? Binds a yabasic-program and the yabasic-interpreter together in
to a
standalone program.
box ? draw a rectangle. A synonym for rectangle
break ? breaks out of one or more loops or switch statements
Name
color ? change color for background of graphic window
Synopsis
backcolour red,green,blue
backcolour "red,green,blue"
Description
Change the color, that becomes visible, if any portion of the window is
erased,
e.g. after clear window or clear line. Note however, that parts of the w
indow,
that display the old background color will not change.
As with the color-command, the new background color can either be specif
ied as
a triple of three numbers or as a single string, that contains those thr
ee
numbers separated by commas.
Example
open window 255,255
for x=10 to 235 step 10:for y=10 to 235 step 10
backcolour x,y,0
clear window
sleep 1
next y:next x
This changes the background colour of the graphic window repeatedly and
clears
it every time, so that it is filled with the new background colour.
See also
open window, color, line, rectangle, triangle, circle
------------------------------------------------------------------------
-------
Name
backcolour ? see backcolor
Synopsis
backcolour red,green,blue
backcolour "red,green,blue"
See also
color
------------------------------------------------------------------------
-------
Name
beep ? ring the bell within your computer; a synonym for bell
Synopsis
beep
Description
The bell-command rings the bell within your computer once. This command
is not
a sound-interface, so you can neither vary the length or the height of t
he
sound (technically, it just prints \a). bell is exactly the same as beep
.
Example
beep:print "This is a problem ..."
See also
beep
------------------------------------------------------------------------
-------
Name
bell ? ring the bell within your computer (just as beep)
Synopsis
bell
Description
The beep-command rings the bell within your computer once. beep is a syn
onym
for bell.
Example
print "This is a problem ...":beep
See also
bell
------------------------------------------------------------------------
-------
Name
bin$() ? converts a number into a sequence of binary digits
Synopsis
hexadecimal$=bin$(decimal)
Description
The bin$-function takes a single numeric argument an converts it into a
string
of binary digits (i.e. zeroes and ones). If you pass a negative number t
o bin$,
the resulting string will be preceded by a '-'.
If you want to convert the other way around (i.e. from binary to decimal
) you
may use the dec-function.
Example
for a=1 to 100
print bin$(a)
next a
This example prints the binary representation of all digits between 1 an
d 100.
See also
hex$, dec
------------------------------------------------------------------------
-------
Name
bind() ? Binds a yabasic-program and the yabasic-interpreter together in
to a
standalone program.
Synopsis
bind("foo.exe")
Description
The bind-command combines your own yabasic-program (plus all the librari
es it
does import) and the interpreter by copying them into a new file, whose
name is
passed as an argument. This new program may then be executed on any comp
uter,
even if it does not have yabasic installed.
Please see the section about creating a standalone-program for details.
Example
if (!peek("isbound")) then
bind "foo"
print "Successfully created the standalone executable 'foo' !"
exit
endif
print "Hello World !"
This example creates a standalone program foo from itself.
See also
The section about creating a standalone-program, the peek-function and t
he
command line options.
------------------------------------------------------------------------
-------
Name
box ? draw a rectangle. A synonym for rectangle
Synopsis
See the rectangle-command.
Description
The box-command does exactly the same as the rectangle-command; it is ju
st a
synonym. Therefore you should refer to the entry for the rectangle-comma
nd for
further information.
------------------------------------------------------------------------
-------
Name
break ? breaks out of one or more loops or switch statements
Synopsis
break
break 2
Description
break transfers control immediately outside the enclosing loop or switch
statement. This is the preferred way of leaving a such a statement (rath
er than
goto, which is still possible in most cases). An optional digit allows o
ne to
break out of multiple levels, e.g. to leave a loop from within a switch
statement. Please note, that only a literal (e.g. 2) is allowed at this
location.
Example
for a=1 to 10
break
print "Hi"
next a
while(1)
break
print "Hi"
wend
repeat
break
print "Hi"
until(0)
switch 1
case 1:break
case 2:case 3:print "Hi"
end switch
This example prints nothing at all, because each of the loops (and the
switch-statement) does an immediate break (before it could print any "Hi
").
See also
for, while, repeat and switch.
C
case ? mark the different cases within a switch-statement
ceil() ? compute the ceiling for its (float) argument.
chomp$() ? Remove a single trailing newline from its string-argument; if
the
string does not end in a newline, the string is returned unchanged.
chr$() ? accepts a number and returns the character at this position wit
hin the
ascii charset
circle ? draws a circle in the graphic-window
clear ? Erase circles, rectangles or triangles
clear screen ? erases the text window
clear window ? clear the graphic window and begin a new page, if printin
g is
under way
close ? close a file, which has been opened before
close curve ? close a curve, that has been drawn by the line-command
close printer ? stops printing of graphics
close window ? close the graphics-window
color ? change color for any subsequent drawing-command
colour ? see color
compile ? compile a string with yabasic-code on the fly
continue ? start the next iteration of a for-, do-, repeat- or while-loo
p
cos() ? return the cosine of its single argument
Name
case ? mark the different cases within a switch-statement
Synopsis
switch a
case 1
case 2
?
end switch
?
switch a$
case "a"
case "b"
?
end switch
Description
Please see the switch-statement.
Example
input a
switch(a)
case 1:print "one":break
case 2:print "two":break
default:print "more"
end switch
Depending on your input (a number is expected) this code will print one
or two
or otherwise more.
See also
switch
------------------------------------------------------------------------
-------
Name
ceil() ? compute the ceiling for its (float) argument.
Synopsis
print ceil(x)
Description
The ceil-function returns the smallest integer number, that is larger or
equal
than its argument.
Example
print ceil(1.5),floor(1.5)
print ceil(2),floor(2)
Comparing functions ceil and floor, gives a first line of output (1 2),
showing
that ceil is less or equal than floor; but as the second line of output
(2 2)
shows, the two functions give equal results for integer arguments.
See also
floor, int, frac
------------------------------------------------------------------------
-------
Name
chomp$() ? Remove a single trailing newline from its string-argument; if
the
string does not end in a newline, the string is returned unchanged.
Synopsis
print chomp$("Hallo !\n")
Description
The chomp$-function checks, if its string-argument ends in a newline and
removes it eventually; for this purpose chomp$ can replace an if-stateme
nt.
This can be especially useful, when you deal with input from external so
urces
like system$.
You may apply chomp$ freely, as it only acts, if there is a newline to r
emove;
note however, that user-input, that comes from the normal input-statemen
t, does
not need such a treatment, because it already comes without a newline.
Example
The following yabasic-program uses the unix-command whoami to get the us
ername
of the current user in order to greet him personally. This is done twice
: First
with the chomp$-function and then again with with an equivalent if-state
ment:
print "Hello " + chomp$(system$("whoami")) + " !"
user$ = system$("whoami")
if (right$(user$,1)="\n") user$=left$(user$,len(user$)-1)
print "Hello again " + user$ + " !"
See also
system$
------------------------------------------------------------------------
-------
Name
chr$() ? accepts a number and returns the character at this position wit
hin the
ascii charset
Synopsis
character$=chr$(ascii)
Description
The chr$-function is the opposite of the asc-function. It looks up and r
eturns
the character at the given position within the ascii-charset. It's typic
al use
is to construct nonprintable characters which do not occur on your keybo
ard.
Nevertheless you won't use chr$ as often as you might think, because the
most
important nonprintable characters can be constructed using escape-sequen
ces
using the \-character (e.g. you might use \n instead of chr$(10) whereve
r you
want to use the newline-character).
Example
print "a",chr$(10),"b"
This will print the letters 'a' and 'b' in different lines because of th
e
intervening newline-character, which is returned by chr$(10).
See also
asc
------------------------------------------------------------------------
-------
Name
circle ? draws a circle in the graphic-window
Synopsis
circle x,y,r
clear circle x,y,r
fill circle x,y,r
clear fill circle x,y,r
Description
The circle-command accepts three parameters: The x- and y-coordinates of
the
center and the radius of the circle.
Some more observations related with the circle-command:
* The graphic-window must have been opened already.
* The circle may well extend over the boundaries of the window.
* If you have issued open printer before, the circle will finally appe
ar in
the printed hard copy of the window.
* fill circle will draw a filled (with black ink) circle.
* clear circle will erase (or clear) the outline of the circle.
* clear fill circle or fill clear circle will erase the full area of t
he
circle.
Example
open window 200,200
for n=1 to 2000
x=ran(200)
y=ran(200)
fill circle x,y,10
clear fill circle x,y,8
next n
This code will open a window and draw 2000 overlapping circles within. E
ach
circle is drawn in two steps: First it is filled with black ink (fill ci
rcle
x,y,10), then most of this circle is erased again (clear fill circle x,y
,8). As
a result each circle is drawn with an opaque white interior and a 2-pixe
l
outline (2-pixel, because the radii differ by two).
See also
open window, open printer, line, rectangle, triangle
------------------------------------------------------------------------
-------
Name
clear ? Erase circles, rectangles or triangles
Synopsis
clear rectangle 10,10,90,90
clear fill circle 50,50,20
clear triangle 10,10,20,20,50,30
Description
May be used within the circle, rectangle or triangle command and causes
these
shapes to be erased (i.e. be drawn in the colour of the background).
fill can be used in conjunction with and wherever the fill-clause may ap
pear.
Used alone, clear will erase the outline (not the interior) of the shape
(circle, rectangle or triangle); together with fill the whole shape (inc
luding
its interior) is erased.
Example
open window 200,200
fill circle 100,100,50
clear fill rectangle 10,10,90,90
This opens a window and draws a pacman-like figure.
See also
clear, circle, rectangle, triangle
------------------------------------------------------------------------
-------
Name
clear screen ? erases the text window
Synopsis
clear screen
Description
clear screen erases the text window (the window where the output of prin
t
appears).
It must be issued at least once, before some advanced screen-commands (e
.g.
print at or inkey$) may be called; this requirement is due to some limit
ations
of the curses-library, which is used by yabasic under Unix for some comm
ands.
Example
clear screen
print "Please press a key : ";
a$=inkey$
print a$
The clear screen command is essential here; if it would be omitted, yaba
sic
would issue an error ("need to call 'clear screen' first") while trying
to
execute the inkey$-function.
See also
inkey$
------------------------------------------------------------------------
-------
Name
clear window ? clear the graphic window and begin a new page, if printin
g is
under way
Synopsis
clear window
Description
clear window clears the graphic window. If you have started printing the
graphic via open printer, the clear window-command starts a new page as
well.
Example
open window 200,200
open printer "t.ps"
for a=1 to 10
if (a>1) clear window
text 100,100,"Hallo "+str$(a)
next a
close printer
close window
This example prints 10 pages, with the text "Hello 1", "Hello 2", ? and
so on.
The clear screen-command clears the graphics window and starts a new pag
e.
See also
open window, open printer
------------------------------------------------------------------------
-------
Name
close ? close a file, which has been opened before
Synopsis
close filenum
close # filenum
Description
The close-command closes an open file. You should issue this command as
soon as
you are done with reading from or writing to a file.
Example
open "my.data" for reading as 1
input #1 a
print a
close 1
This program opens the file "my.data", reads a number from it, prints th
is
number and closes the file again.
See also
open
------------------------------------------------------------------------
-------
Name
close curve ? close a curve, that has been drawn by the line-command
Synopsis
new curve
line to x1,y1
?
close curve
Description
The close curve-command closes a sequence of lines, that has been drawn
by
repeated line to-commands.
Example
open window 200,200
new curve
line to 100,50
line to 150,150
line to 50,150
close curve
This example draws a triangle: The three line to-commands draw two lines
; the
final line is however not drawn explicitly, but drawn by the close
curve-command.
See also
line, new curve
------------------------------------------------------------------------
-------
Name
close printer ? stops printing of graphics
Synopsis
close printer
Description
The close printer-command ends the printing graphics. Between open print
er and
close printer everything you draw (e.g. circles, lines ?) is sent to you
r
printer. close printer puts an end to printing and will make your printe
r eject
the page.
Example
open window 200,200
open printer
circle 100,100,50
close printer
close window
As soon as close printer is executed, your printer will eject a page wit
h a
circle on it.
See also
open printer
------------------------------------------------------------------------
-------
Name
close window ? close the graphics-window
Synopsis
close window
Description
The close window-command closes the graphics-window, i.e. it makes it di
sappear
from your screen. It includes an implicit close printer, if a printer ha
s been
opened previously.
Example
open window 200,200
circle 100,100,50
close window
This example will open a window, draw a circle and close the window agai
n; all
this without any pause or delay, so the window will be closed before you
may
regard the circle..
See also
open window
------------------------------------------------------------------------
-------
Name
color ? change color for any subsequent drawing-command
Synopsis
colour red,green,blue
colour "red,green,blue"
Description
Change the color, in which lines, dots, circles, rectangles or triangles
are
drawn. The color-command accepts three numbers in the range 0 ? 255 (as
in the
first line of the synopsis above). Those numbers specify the intensity f
or the
primary colors red, green and blue respectively. As an example 255,0,0 i
s red
and 255,255,0 is yellow.
Alternatively you may specify the color with a single string (as in the
second
line of the synopsis above); this string should contain three numbers,
separated by commas. As an example "255,0,255" would be violet. Using th
is
variant of the colour-command, you may use symbolic names for colours:
open window 100,100
yellow$="255,255,0"
color yellow$
text 50,50,"Hallo"
, which reads much clearer.
Example
open window 255,255
for x=10 to 235 step 10:for y=10 to 235 step 10
colour x,y,0
fill rectangle x,y,x+10,y+10
next y:next x
This fills the window with colored rectangles. However, none of the used
colours contains any shade of blue, because the color-command has always
0 as a
third argument.
See also
open window, backcolor, line, rectangle, triangle, circle
------------------------------------------------------------------------
-------
Name
colour ? see color
Synopsis
colour red,green,blue
colour "red,green,blue"
See also
color
------------------------------------------------------------------------
-------
Name
compile ? compile a string with yabasic-code on the fly
Synopsis
compile(code$)
Description
This is an advanced command (closely related with the execute-command).
It
allows you to compile a string of yabasic-code (which is the only argume
nt).
Afterwards the compiled code is a normal part of your program.
Note, that there is no way to remove the compiled code.
Example
compile("sub mysub(a):print a:end sub")
mysub(2)
This example creates a function named mysub, which simply prints its sin
gle
argument.
See also
execute
------------------------------------------------------------------------
-------
Name
continue ? start the next iteration of a for-, do-, repeat- or while-loo
p
Synopsis
continue
Description
You may use continue within any loop to start the next iteration immedia
tely.
Depending on the type of the loop, the loop-condition will or will not b
e
checked. Especially: for- and while-loops will evaluate their respective
conditions, do- and repeat-loops will not.
Remark: Another way to change the flow of execution within a loop, is th
e
break-command.
Example
for a=1 to 100
if mod(a,2)=0 continue
print a
next a
This example will print all odd numbers between 1 and 100.
See also
for, do, repeat, while, break
------------------------------------------------------------------------
-------
Name
cos() ? return the cosine of its single argument
Synopsis
x=cos(angle)
Description
The cos-function expects an angle (in radians) and returns its cosine.
Example
print cos(pi)
This example will print -1.
See also
acos, sin
D
data ? introduces a list of data-items
date$ ? returns a string with various components of the current date
dec() ? convert a base 2 or base 16 number into decimal form
default ? mark the default-branch within a switch-statement
dim ? create an array prior to its first use
do ? start a (conditionless) do-loop
doc ? special comment, which might be retrieved by the program itself
docu$ ? special array, containing the contents of all docu-statement wit
hin the
program
dot ? draw a dot in the graphic-window
Name
data ? introduces a list of data-items
Synopsis
data 9,"world"
?
read b,a$
Description
The data-keyword introduces a list of comma-separated list of strings or
numbers, which may be retrieved with the read-command.
The data-command itself does nothing; it just stores data. A single
data-command may precede an arbitrarily long list of values, in which st
rings
or numbers may be mixed at will.
yabasic internally uses a data-pointer to keep track of the current loca
tion
within the data-list; this pointer may be reset with the restore-command
.
Example
do
restore
for a=1 to 4
read num$,num
print num$,"=",num
next a
loop
data "eleven",11,"twelve",12,"thirteen",13,"fourteen",14
This example just prints a series of lines eleven=11 up to fourteen=14 a
nd so
on without end.
The restore-command ensures that the list of data-items is read from the
start
with every iteration.
See also
read, restore
------------------------------------------------------------------------
-------
Name
date$ ? returns a string with various components of the current date
Synopsis
a$=date$
Description
The date$-function (which must be called without parentheses; i.e. date$
()
would be an error) returns a string containing various components of a d
ate; an
example would be 4-05-27-2004-Thu-May. This string consists of various f
ields
separated by hyphens ("-"):
* The day within the week as a number in the range 0 (=Sunday) to 6 (=
Saturday) (in the example above: 4, i.e. Thursday).
* The month as a number in the range 1 (=January) to 12 (=December) (i
n the
example: 5 which stands for May).
* The day within the month as a number in the range 1 to 31 (in the ex
ample:
27).
* The full, 4-digit year (in the example: 2004, which reminds me that
I
should adjust the clock within my computer ?).
* The abbreviated name of the day within the week (Mon to Sun).
* The abbreviated name of the month (Jan to Dec).
Therefore the whole example above (4-05-27-2004-Thu-May) would read: day
4 in
the week (counting from 0), May 27 in the year 2004, which is a Thursday
in
May.
Note, that all fields within the string returned by date$ have a fixed w
ith
(numbers are padded with zeroes); therefore it is easy to extract the va
rious
fields of a date format with mid$.
Example
rem Two ways to print the same ...
print mid$(date$,3,10)
dim fields$(6)
a=split(date$,fields$(),"-")
print fields$(2),"-",fields$(3),"-",fields$(4)
This example shows two different techniques to extract components from t
he
value returned by date$. The mid$-function is the preferred way, but you
could
just as well split the return-value of date$ at every "-" and store the
result
within an array of strings.
See also
time$
------------------------------------------------------------------------
-------
Name
dec() ? convert a base 2 or base 16 number into decimal form
Synopsis
a=dec(number$)
a=dec(number$,base)
Description
The dec-function takes the string-representation of a base-2 or base-16
(which
is the default) number and converts it into a decimal number. The option
al
second argument (base) might be used to specify a base other than 16. Ho
wever,
currently only base 2 or base 16 are supported. Please note, that for ba
se 16
you may write literals in the usual way, by preceding them with 0x, e.g.
like
print 0xff
; this may save you from applying the dec altogether.
Example
input "Please enter a binary number: " a$
print a$," is ",dec(a$)
See also
bin$, hex$
------------------------------------------------------------------------
-------
Name
default ? mark the default-branch within a switch-statement
Synopsis
switch a+3
case 1
?
case 2
?
default
?
end switch
Description
The default-clause is an optional part of the switch-statement (see ther
e for
more information). It introduces a series of statements, that should be
executed, if none of the cases matches, that have been specified before
(each
with its own case-clause).
So default specifies a default to be executed, if none of the explicitly
named
cases matches; hence its name.
Example
print "Please enter a number between 0 and 6,"
print "specifying a day in the week."
input d
switch d
case 0:print "Monday":break
case 1:print "Tuesday":break
case 2:print "Wednesday":break
case 3:print "Thursday":break
case 4:print "Friday":break
case 5:print "Saturday":break
case 6:print "Sunday":break
default:print "Hey you entered something invalid !"
end switch
This program translates a number between 0 and 6 into the name of a week
day;
the default-case is used to detect (and complain about) invalid input.
See also
sub, case
------------------------------------------------------------------------
-------
Name
dim ? create an array prior to its first use
Synopsis
dim array(x,y)
dim array$(x,y)
Description
The dim-command prepares one or more arrays (of either strings or number
s) for
later use. This command can also be used to enlarges an existing array.
When an array is created with the dim-statement, memory is allocated and
all
elements are initialized with either 0 (for numerical arrays) or "" (for
string
arrays).
If the array already existed, and the dim-statement specifies a larger s
ize
than the current size, the array is enlarged and any old content is pres
erved.
Note, that dim cannot be used to shrink an array: If you specify a size,
that
is smaller than the current size, the dim-command does nothing.
Finally: To create an array, that is only known within a single subrouti
ne, you
should use the command local, which creates local variables as well as l
ocal
arrays.
Example
dim a(5,5)
for x=1 to 5:for y=1 to 5
a(x,y)=int(ran(100))
next y:next x
printmatrix(a())
dim a(7,7)
printmatrix(a())
sub printmatrix(ar())
local x,y,p,q
x=arraysize(ar(),1)
y=arraysize(ar(),2)
for q=1 to y
for p=1 to y
print ar(p,q),"\t";
next p
print
next q
end sub
This example creates a 2-dimensional array (i.e. a matrix) with the
dim-statement and fills it with random numbers. The second dim-statement
enlarges the array, all new elements are filled with 0.
The subroutine printmatrix just does, what its name says.
See also
arraysize, arraydim, local
------------------------------------------------------------------------
-------
Name
do ? start a (conditionless) do-loop
Synopsis
do
?
loop
Description
Starts a loop, which is terminated by loop; everything between do and lo
op will
be repeated forever. This loop has no condition, so it is an infinite lo
op;
note however, that a break- or goto-statement might be used to leave thi
s loop
anytime.
Example
do
a=a+1
print a
if (a>100) break
loop
This example prints the numbers between 1 and 101. The break-statement i
s used
to leave the loop.
See also
loop, repeat, while, break
------------------------------------------------------------------------
-------
Name
doc ? special comment, which might be retrieved by the program itself
Synopsis
doc This is a comment
docu This is another comment
Description
Introduces a comment, which spans up to the end of the line. But other t
han the
rem-comment, any docu-comment is collected within the special docu$-arra
y and
might be retrieved later on. Moreover you might invoke yabasic -docu foo
.yab on
the command line to retrieve the embedded documentation within the progr
am
foo.yab.
Instead of doc you may just as well write docu or even documentation.
Example
rem Hi, this has been written by me
rem
doc This program asks for a number and
doc prints this number multiplied with 2
rem
rem Print out rhe above message
for a=1 to arraysize(docu$()):print docu$(a):next a
rem Read and print the number
input "Please input a number: " x
print x*2
This program uses the comments within its code to print out a help messa
ge for
the user.
The contents of the doc-lines are retrieved from the docu$-array; if you
do not
want a comment to be collected within this array, use the rem-statement
instead.
See also
docu$, rem
------------------------------------------------------------------------
-------
Name
docu$ ? special array, containing the contents of all docu-statement wit
hin the
program
Synopsis
a$=docu$(1)
Description
Before your program is executed, yabasic collects the content of all the
doc-statements within your program within this 1-dimensional array (well
only
those within the main-program, libraries are skipped).
You may use the arraysize function to find out, how many lines it contai
ns.
Example
docu
docu This program reads two numbers
docu and adds them.
docu
rem retrieve and print the embedded documentation
for a=1 to arraysize(docu$(),1)
print docu$(a)
next a
input "First number: " b
input "Second number: " c
print "The sum of ",b," and ",c," is ",b+c
This program uses the embedded documentation to issue a usage-message.
See also
arraydim, rem
------------------------------------------------------------------------
-------
Name
dot ? draw a dot in the graphic-window
Synopsis
dot x,y
clear dot x,y
Description
Draws a dot at the specified coordinates within your graphic-window. If
printing is in effect, the dot appears on your printout too.
Use the functions peek("winheight") or peek("winwidth") to get the size
of your
window and hence the boundaries of the coordinates specified for the
dot-command.
Example
open window 200,200
circle 100,100,100
do
x=ran(200):y=ran(200)
dot x,y
total=total+1
if (sqrt((x-100)^2+(y-100)^2)<100) in=in+1
print 4*in/total
loop
This program uses a well known algorithm to compute ?.
See also
line, open window
E
else ? mark an alternative within an if-statement
elsif ? starts an alternate condition within an if-statement
end ? terminate your program
endif ? ends an if-statement
end sub ? ends a subroutine definition
eof ? check, if an open file contains data
eor() ? compute the bitwise exclusive or of its two arguments
error ? raise an error and terminate your program
euler ? another name for the constant 2.71828182864
execute$() ? execute a user defined subroutine, which must return a stri
ng
execute() ? execute a user defined subroutine, which must return a numbe
r
exit ? terminate your program
exp() ? compute the exponential function of its single argument
export ? mark a function as globally visible
Name
else ? mark an alternative within an if-statement
Synopsis
if (?) then
?
else
?
endif
Description
The else-statement introduces the alternate branch of an if-statement. I
.e. it
starts the sequence of statements, which is executed, if the condition o
f the
if-statement is not true.
Example
input "Please enter a number: " a
if (mod(a,2)=1) then
print a," is odd."
else
print a," is even."
endif
This program detects, if the number you have entered is even or odd.
See also
if
------------------------------------------------------------------------
-------
Name
elsif ? starts an alternate condition within an if-statement
Synopsis
if (?) then
?
elseif (?)
?
elsif (?) then
?
else
?
endif
Description
The elsif-statement is used to select a single alternative among a serie
s of
choices.
With each elsif-statement you may specify a condition, which is tested,
if the
main condition (specified with the if-statement) has failed. Note that e
lsif
might be just as well written as elseif.
Within the example below, two variables a and b are tested against a ran
ge of
values. The variable a is tested with the elsif-statement. The very same
tests
are performed for the variable b too; but here an involved series of
if-else-statements is employed, making the tests much more obscure.
Example
input "Please enter a number: " a
if (a<0) then
print "less than 0"
elseif (a<=10) then
print "between 0 and 10"
elsif (a<=20)
print "between 11 and 20"
else
print "over 20"
endif
input "Please enter another number: " b
if (b<0) then
print "less than 0"
else
if (b<=10) then
print "between 0 and 10"
else
if (b<=20) then
print "between 11 and 20"
else
print "over 20"
endif
endif
endif
Note, that the very same tests are performed for the variables a and b,
but can
be stated much more clearly with the elsif-statement.
Note, that elsif might be written as elseif too, and that the keyword th
en is
optional.
See also
if, else
------------------------------------------------------------------------
-------
Name
end ? terminate your program
Synopsis
end
Description
Terminate your program. Much (but not exactly) like the exit command.
Note, that end may not end your program immediately; if you have opened
a
window or called clear screen, yabasic assumes, that your user wants to
study
the output of your program after it has ended; therefore it issues the l
ine
---Program done, press RETURN--- and waits for a key to be pressed. If y
ou do
not like this behaviour, consider using exit.
Example
print "Do you want to continue ?"
input "Please answer y(es) or n(o): " a$
if (lower$(left$(a$,1))="n") then
print "bye"
end
fi
See also
exit
------------------------------------------------------------------------
-------
Name
endif ? ends an if-statement
Synopsis
if (?) then
?
endif
Description
The endif-statement closes (or ends) an if-statement.
Note, that endif may be written in a variety of other ways: end if, end-
if or
even fi.
The endif-statement must be omitted, if the if-statement does not contai
n the
keyword then (see the example below). Such an if-statement without endif
extends only over a single line.
Example
input "A number please: " a
if (a<10) then
print "Your number is less than 10."
endif
REM and now without endif
input "A number please: " a
if (a<10) print "Your number is less than 10."
See also
if
------------------------------------------------------------------------
-------
Name
end sub ? ends a subroutine definition
Synopsis
sub foo(?)
?
end sub
Description
Marks the end of a subroutine-definition (which starts with the sub-keyw
ord).
The whole concept of subroutines is explained within the entry for sub.
Example
print foo(3)
sub foo(a)
return a*2
end sub
This program prints out 6. The subroutine foo simply returns twice its
argument.
See also
sub
------------------------------------------------------------------------
-------
Name
eof ? check, if an open file contains data
Synopsis
open 1,"foo.bar"
if (eof(1)) then
?
end if
Description
The eof-function checks, if there is still data left within an open file
. As an
argument it expects the file-number as returned by (or used within) the
open-function (or statement).
Example
a=open("foo.bar")
while(not eof(a))
input #a,a$
print a$
end while
This example will print the contents of the file "foo.bar". The eof-func
tion
will terminate the loop, if there is no more data left within the file.
See also
open
------------------------------------------------------------------------
-------
Name
eor() ? compute the bitwise exclusive or of its two arguments
Synopsis
print eor(a,b)
Description
The eor-function takes two arguments and computes their bitwise exclusiv
e or.
See your favorite introductory text on informatics for an explanation of
this
function.
The xor-function is the same as the eor function; both are synonymous; h
owever
they have each their own description, so you may check out the entry of
xor for
a slightly different view.
Example
for a=0 to 3
for b=0 to 3
print fill$(bin$(a))," eor ",fill$(bin$(b))," = ",fill$(bin$(eor(a,b
)))
next b
next a
sub fill$(a$)
return right$("0"+a$,2)
end sub
This example prints a table, from which you may figure, how the eor-func
tion is
computed.
See also
and, or
------------------------------------------------------------------------
-------
Name
error ? raise an error and terminate your program
Synopsis
error "Wrong, wrong, wrong !!"
Description
Produces the same kind or error messages, that yabasic itself produces (
e.g. in
case of a syntax-error). The single argument is issued along with the cu
rrent
line-number.
Example
input "Please enter a number between 1 and 10: " a
if (a<1 or a>10) error "Oh no ..."
This program is very harsh in checking the users input; instead of just
asking
again, the program terminates with an error, if the user enters somethin
g
wrong.
The error message would look like this:
---Error in t.yab, line 2: Oh no ...
---Error: Program stopped due to an error
See also
Well, there should be a corresponding called warning; unfortunately ther
is
none yet.
------------------------------------------------------------------------
-------
Name
euler ? another name for the constant 2.71828182864
Synopsis
foo=euler
Description
euler is the well known constant named after Leonard Euler; its value is
2.71828182864. euler is not a function, so parens are not allowed (i.e.
euler()
will produce an error). Finally, you may not assign to euler; it wouldn'
t sense
anyway, because it is a constant.
Example
print euler
See also
pi
------------------------------------------------------------------------
-------
Name
execute$() ? execute a user defined subroutine, which must return a stri
ng
Synopsis
print execute$("foo$","arg1","arg2")
Description
execute$ can be used to execute a user defined subroutine, whose name ma
y be
specified as a string expression.
This feature is the only way to execute a subroutine, whose name is not
known
by the time you write your program. This might happen, if you want to ex
ecute a
subroutine, which is compiled (using the compile command) during the cou
rse of
execution of your program.
Note however, that the execute$-function is not the preferred method to
execute
a user defined subroutine; in almost all cases you should just execute a
subroutine by writing down its name within your yabasic program (see the
example).
Example
print execute$("foo$","Hello","world !")
sub foo$(a$,b$)
return a$+" "+b$
end sub
The example simply prints Hello world !, which is the return value of th
e user
defined subroutine foo$. The same could be achieved by executing:
print foo$(a$,b$)
See also
compile, execute
------------------------------------------------------------------------
-------
Name
execute() ? execute a user defined subroutine, which must return a numbe
r
Synopsis
print execute("bar","arg1","arg2")
Description
The execute-function is the counterpart of the execute$-function (please
see
there for some caveats). execute executes subroutines, which returns a n
umber.
Example
print execute("bar",2,3)
sub bar(a,b)
return a+b
end sub
See also
compile, execute$
------------------------------------------------------------------------
-------
Name
exit ? terminate your program
Synopsis
exit
exit 1
Description
Terminate your program and return any given value to the operating syste
m. exit
is similar to end, but it will terminate your program immediately, no ma
tter
what.
Example
print "Do you want to continue ?"
input "Please answer y(es) or n(o): " a$
if (lower$(left$(a$,1))="n") exit 1
See also
end
------------------------------------------------------------------------
-------
Name
exp() ? compute the exponential function of its single argument
Synopsis
foo=exp(bar)
Description
This function computes e to the power of its argument, where e is the we
ll
known euler constant 2.71828182864.
The exp-function is the inverse of the log-function.
Example
open window 100,100
for x=0 to 100
dot x,100-100*exp(x/100)/euler
next x
This program plots part of the exp-function, however the range is rather
small,
so that you may not recognize the function from this plot.
See also
log
------------------------------------------------------------------------
-------
Name
export ? mark a function as globally visible
Synopsis
export sub foo(bar)
?
end sub
Description
The export-statement is used within libraries to mark a user defined sub
routine
as visible outside the library wherein it is defined. Subroutines, which
are
not exported, must be qualified with the name of the library, e.g. foo.b
az
(where foo is the name of the library and baz the name of the subroutine
);
exported subroutines may be used without specifying the name of the libr
ary,
e.g. bar.
Therefore export may only be useful within libraries.
Example
The library foo.bar (which is listed below) defines two functions bar an
d baz,
however only the function bar is exported and therefore visible even out
side
the library; baz is not exported and may only be used within the library
foo.yab:
export sub bar()
print "Hello"
end sub
sub baz()
print "World"
end sub
Now within your main program cux.yab (which imports the library foo.yab)
; note
that this program produces an error:
import foo
print "Calling subroutine foo.bar (okay) ..."
foo.bar()
print "done."
print "Calling subroutine bar (okay) ..."
bar()
print "done."
print "Calling subroutine foo.baz (okay) ..."
foo.baz()
print "done."
print "Calling subroutine baz (NOT okay) ..."
baz()
print "done."
The output when executing yabasic foo.yab is this:
Calling subroutine foo.bar (okay) ...
Hello
done.
Calling subroutine bar (okay) ...
Hello
done.
Calling subroutine foo.baz (okay) ...
World
done.
Calling subroutine baz (NOT okay) ...
---Error in main.yab, line 16: can't find subroutine 'baz'
---Dump: sub baz() called in main.yab,16
---Error: Program stopped due to an error
As the error message above shows, the subroutine baz must be qualified w
ith the
name of the library, if used outside the library, wherein it is defined
(e.g.
foo.baz. I.e. outside the library foo.yab you need to write foo.baz. baz
alone
would be an error.
The subroutine bar (without adding the name of the library) however may
(and
probably should) be used in any program, which imports the library foo.y
ab.
Note
In some sense the set of exported subroutines constitutes the interface
of a
library.
See also
sub, import
F
false ? a constant with the value of 0
fi ? another name for endif
fill ? draw a filled circles, rectangles or triangles
floor() ? compute the floor for its (float) argument.
for ? starts a for-loop
frac() ? return the fractional part of its numeric argument
Name
false ? a constant with the value of 0
Synopsis
okay=false
Description
The constant false can be assigned to variables which later appear in
conditions (e.g. within an if-statement.
false may also be written as FALSE or even FaLsE.
Example
input "Please enter a number between 1 and 10: " a
if (check_input(a)) print "Okay"
sub check_input(x)
if (x>10 or x<1) return false
return true
end sub
The subroutine check_input checks its argument and returns true or false
according to the outcome of the check..
See also
true
------------------------------------------------------------------------
-------
Name
fi ? another name for endif
Synopsis
if (?)
?
fi
Description
fi marks the end of an if-statement and is exactly equivalent to endif,
please
see there for further information.
Example
input "A number please: " a
if (a<10) then
print "Your number is less than 10."
fi
See also
endif
------------------------------------------------------------------------
-------
Name
fill ? draw a filled circles, rectangles or triangles
Synopsis
fill rectangle 10,10,90,90
fill circle 50,50,20
fill triangle 10,20,20,10,20,20
Description
The keyword fill may be used within the circle, rectangle or triangle co
mmand
and causes these shapes to be filled.
fill can be used in conjunction with and wherever the clear-clause may a
ppear.
Used alone, fill will fill the interior of the shape (circle, rectangle
or
triangle); together with clear the whole shape (including its interior)
is
erased.
Example
open window 200,200
fill circle 100,100,50
clear fill rectangle 10,10,90,90
This opens a window and draws a pacman-like figure.
See also
clear, circle, rectangle, triangle
------------------------------------------------------------------------
-------
Name
floor() ? compute the floor for its (float) argument.
Synopsis
print floor(x)
Description
The floor-function returns the largest integer number, that is smaller o
r equal
than its argument. For positive numbers x, floor(x) is the same as int(x
); for
negaive numbers it can be different (see the example below).
Example
print int(-1.5),floor(-1.5)
print int(-1),floor(-1)
print int(1.5),floor(1.5)
This example compares the functions int and floor, starting with -1 -2,
then -1
-1 and ending with 1 1, which shows the different behaviour of both func
tions.
See also
ceil, int, frac
------------------------------------------------------------------------
-------
Name
for ? starts a for-loop
Synopsis
for a=1 to 100 step 2
?
next a
Description
The for-loop lets its numerical variable (a in the synopsis) assume all
values
within the given range. The optional step-clause may specify a value (de
fault:
1) by which the variable will be incremented (or decremented, if step is
negative).
Any for-statement can be replaced by a set of ifs and gotos; as you may
infer
from the example below this is normally not feasible. However if you wan
t to
know in detail how the for-statement works, you should study this exampl
e,
which presents a for-statement and an exactly equivalent series of ifs a
nd
gotos.
Example
for a=1 to 10 step 2:print a:next
a=1
label check
if (a>10) goto done
print a
a=a+2
goto check
label done
This example simply prints the numbers 1, 3, 5, 7 and 9. It does this tw
ice:
First with a simple for-statement and then with ifs and gotos.
See also
step, next
------------------------------------------------------------------------
-------
Name
frac() ? return the fractional part of its numeric argument
Synopsis
x=frac(y)
Description
The frac-function takes its argument, removes all the digits to the left
of the
comma and just returns the digits right of the comma, i.e. the fractiona
l part.
Refer to the example to learn how to rewrite frac by employing the int-f
unction
(which is not suggested anyway).
Example
for a=1 to 10
print frac(sqr(a))
print sqr(a)-int(sqr(a))
next a
The example prints the fractional part of the square root of the numbers
between 1 and 10. Each result is computed (and printed) twice: Once by
employing the frac-function and once by employing the int-function.
See also
int, floor, ceil
G
getbit$() ? return a string representing the bit pattern of a rectangle
within
the graphic window
getscreen$() ? returns a string representing a rectangular section of th
e text
terminal
glob() ? check if a string matches a simple pattern
gosub ? continue execution at another point within your program (and ret
urn
later)
goto ? continue execution at another point within your program (and neve
r come
back)
Name
getbit$() ? return a string representing the bit pattern of a rectangle
within
the graphic window
Synopsis
a$=getbit$(10,10,20,20)
a$=getbit$(10,10 to 20,20)
Description
The function getbit returns a string, which contains the encoded bit-pat
tern of
a rectangle within graphic window; the four arguments specify two opposi
te
corners of the rectangle. The string returned might later be fed to the
putbit
-command.
The getbit$-function might be used for simple animations (as in the exam
ple
below).
Example
open window 40,40
fill circle 20,20,18
circle$=getbit$(0,0,40,40)
close window
open window 200,200
for x=1 to 200
putbit circle$,x,80
next x
This example features a circle moving from left to right over the window
.
See also
putbit
------------------------------------------------------------------------
-------
Name
getscreen$() ? returns a string representing a rectangular section of th
e text
terminal
Synopsis
a$=getscreen$(2,2,20,20)
Description
The getscreen$ function returns a string representing the area of the sc
reen as
specified by its four arguments (which specify two opposite corners). I.
e.
everything you have printed within this rectangle will be encoded in the
string
returned (including any colour-information).
Like most other commands dealing with advanced text output, getscreen$
requires, that you have called clear screen before.
Example
clear screen
for a=1 to 1000:
print color("red") "1";
print color("green") "2";
print color("blue") "3";
next a
screen$=getscreen$(10,10,40,10)
print at(10,10) " Please Press 'y' or 'n' ! "
a$=inkey$
putscreen screen$,10,10
This program fills the screen with colored digits and afterwards asks th
e user
for a choice ( Please press 'y' or 'n' ! ). Afterwards the area of the s
creen,
which has been overwritten by the question will be restored with its pre
vious
contents, whhch had been saved via getscreen$.
See also
putscreen$
------------------------------------------------------------------------
-------
Name
glob() ? check if a string matches a simple pattern
Synopsis
if (glob(string$,pattern$)) ?
Description
The glob-function takes two arguments, a string and a (glob-) pattern, a
nd
checks if the string matches the pattern. However glob does not employ t
he
powerful rules of regular expressions; rather it has only two special
characters: * (which matches any number (even zero) of characters) and ?
(which
matches exactly a single character).
Example
for a=1 to 10
read string$,pattern$
if (glob(string$,pattern$)) then
print string$," matches ",pattern$
else
print string$," does not match ",pattern$
endif
next a
data "abc","a*"
data "abc","a?"
data "abc","a??"
data "abc","*b*"
data "abc","*"
data "abc","???"
data "abc","?"
data "abc","*c"
data "abc","A*"
data "abc","????"
This program checks the string abc against various patterns and prints t
he
result. The output is:
abc matches a*
abc does not match a?
abc matches a??
abc matches *b*
abc matches *
abc matches ???
abc does not match ?
abc matches *c
abc does not match A*
abc does not match ????
See also
There are no related commands.
------------------------------------------------------------------------
-------
Name
gosub ? continue execution at another point within your program (and ret
urn
later)
Synopsis
gosub foo
?
label foo
?
return
Description
gosub remembers the current position within your program and then passes
the
flow of execution to another point (which is normally marked with a labe
l).
Later, when a return-statement is encountered, the execution is resumed
at the
previous location.
gosub is the traditional command for calling code, which needs to be exe
cuted
from various places within your program. However, with subroutines yabas
ic
offers a much more flexible way to achieve this (and more). Therefore go
sub
must to be considered obsolete.
Example
print "Do you want to exit ? "
gosub ask
if (r$="y") exit
label ask
input "Please answer yes or no, by typing 'y' or 'n': ",r$
return
See also
return, goto, sub, label, on gosub
------------------------------------------------------------------------
-------
Name
goto ? continue execution at another point within your program (and neve
r come
back)
Synopsis
goto foo
?
label foo
Description
The goto-statement passes the flow of execution to another point within
your
program (which is normally marked with a label).
goto is normally considered obsolete and harmful, however in yabasic it
may be
put to the good use of leaving loops (e.g. while or for) prematurely. No
te
however, that subroutines may not be left with the goto-statement.
Example
print "Please press any key to continue."
print "(program will continue by itself within 10 seconds)"
for a=1 to 10
if (inkey$(1)<>"") then goto done
next a
label done
print "Hello World !"
Here the goto-statement is used to leave the for-loop prematurely.
See also
gosub, on goto
H
hex$() ? convert a number into hexadecimal
Name
hex$() ? convert a number into hexadecimal
Synopsis
print hex$(foo)
Description
The hex$-function converts a number into a string with its hexadecimal
representation. hex$ is the inverse of the dec-function.
Example
open 1,"foo"
while(!eof(1))
print right$("0"+hex$(peek(1)),2)," ";
i=i+1
if (mod(i,10)=0) print
end while
print
This program reads the file foo and prints its output as a hex-dump usin
g the
hex-function.
See also
decbin
I
if ? evaluate a condition and execute statements or not, depending on th
e
result
import ? import a library
inkey$ ? wait, until a key is pressed
input ? read input from the user (or from a file) and assign it to a var
iable
instr() ? searches its second argument within the first; returns its pos
ition
if found
int() ? return the integer part of its single numeric argument
Name
if ? evaluate a condition and execute statements or not, depending on th
e
result
Synopsis
if (?) then
?
endif
if (?) ?
if (?) then
?
else
?
endif
if (?) then
?
elsif (?)
?
elsif (?) then
?
else
?
endif
Description
The if-statement is used to evaluate a conditions and take actions accor
dingly.
(As an aside, please note that there is no real difference between condi
tions
and expressions.)
There are two major forms of the if-statement:
* The one-line-form without the keyword then:
if (?) ?
This form evaluates the condition and if the result is true executes
all
commands (separated by colons) upt to the end of the line. There is
neither
an endif keyword nor an else-branch.
* The multi-line-form with the keyword then:
if (?) then ? elsif (?) ? else ? endif
(where elsif and else are optional, whereas endif is not.
According to the requirements of your program, you may specify:
+ elsif(?), which specifies a condition, that will be evaluated on
ly if
the condition(s) within if or any preceding elsif did not match.
+ else, which introduces a sequence of commands, that will be exec
uted,
if none of the conditions above did match.
+ endif is required and ends the if-statement.
Example
input "Please enter a number between 1 and 4: " a
if (a<=1 or a>=4) error "Wrong, wrong !"
if (a=1) then
print "one"
elsif (a=2)
print "two"
elsif (a=3)
print "three"
else
print "four"
endif
The input-number between 1 and 4 is simply echoed as text (one, two, ?).
The
example demonstrates both forms (short and long) of the if-statement (No
te
however, that the same thing can be done, probably somewhat more elegant
, with
the switch-statement).
See also
else, elsif, endif, conditions and expressions.
------------------------------------------------------------------------
-------
Name
import ? import a library
Synopsis
import foo
Description
The import-statement imports a library. It expects a single argument, wh
ich
must be the name of a library (without the trailing .yab). This library
will
then be read and parsed and its subroutines (and variables) will be made
available within the importing program. Most of the time this will be th
e main
program, but libraries my also import and use other libraries.
Libraries will first be searched in three locations in order:
* The current directory, i.e. the directory from which you have invoke
d
yabasic)
* The directory, where your main program lives. This can be different
from
the first directory, if you specify a path for your main program, e.
g. like
yabasic foo/bar.yab.
* Finally, libraries are searched within a special directory, whose ex
act
location depends on your system or options when invoking yabasic. Ty
pical
values would be /usr/lib under Unix or C:\yabasic\lib under Windows.
Invoking yabasic --help will show the correct directory. The locatio
n of
this directory may be changed with the option --librarypath (see opt
ions).
Example
Lets say you have a yabasic-program foo.yab, which imports a library lib
.yab.
foo.yab; this would read:
import lib
rem This works
lib.x(0)
rem This works too
x(1)
rem And this
lib.y(2)
rem But this not !
y(3)
Now the library lib.yab reads:
rem Make the subroutine x easily available outside this library
export sub x(a)
print a
return
end sub
rem sub y must be referenced by its full name
rem outside this library
sub y(a)
print a
return
end sub
This program produces an error:
0
1
2
---Error in foo.yab, line 13: can't find subroutine 'y'
---Dump: sub y() called in foo.yab,13
---Error: Program stopped due to an error
As you may see from the error message, yabasic is unable to find the sub
routine
y without specifying the name of the library (i.e. lib.y). The reason fo
r this
is, that y, other than x, is not exported from the library lib.yab (usin
g the
export-statement).
See also
export, sub
------------------------------------------------------------------------
-------
Name
inkey$ ? wait, until a key is pressed
Synopsis
clear screen
foo$=inkey$
inkey$
foo$=inkey$(bar)
inkey$(bar)
Description
The inkeys$-function waits, until the user presses a key on the keyboard
or a
button of his mouse, and returns this very key. An optional argument spe
cifies
the number of seconds to wait; if omitted, inkey$ will wait indefinitely
.
inkey$ may only be used, if clear screen has been called at least once.
For normal keys, yabasic simply returns the key, e.g. a, 1 or !. For fun
ction
keys you will get f1, f2 and so on. Other special keys will return these
strings respectively: enter, backspace, del, esc, scrnup (for screen up)
,
scrndown and tab. Modifier keys (e.g. ctrl, alt or shift) by themselves
can not
be detected (e.g. if you simultaneously press shift and 'a', inkey$ will
return
the letter 'A' instead of 'a' of course).
If a graphical window has been opened (via open window) any mouseclick w
ithin
this window will be returned by inkey$ too. The string returned (e.g.
MB1d+0:0028,0061, MB2u+0:0028,0061 or MB1d+1:0028,0061) is constructed a
s
follows:
* Every string associated with a mouseclick will start with the fixed
string
MB
* The next digit (1, 2 or 3) specifies the mousebutton pressed.
* A single letter, d or u, specifies, if the mousebutton has been pres
sed or
released: d stands for down, i.e. the mousebutton has been pressed;
u means
up, i.e. the mousebutton has been released.
* The plus-sign ('+'), which follows is always fixed.
* The next digit (in the range 0 to 7) encodes the modifier keys press
ed,
where 1 stands for shift, 2 stands for alt and 4 stands for ctrl.
* The next four digits (e.g. 0028) contain the x-position, where the
mousebutton has been pressed.
* The comma to follow is always fixed.
* The last four digits (e.g. 0061) contain the y-position, where the
mousebutton has been pressed.
All those fields are of fixed length, so you may use functions like mid$
to
extract certain fields. However, note that with mousex, mousey, mouseb a
nd
mousemod there are specialized functions to return detailed information
about
the mouseclick. Finally it should be noted, that inkey$ will only regist
er
mouseclicks within the graphic-window; mouseclicks in the text-window ca
nnot be
detected.
inkey$ accepts an optional argument, specifying a timeout in seconds; if
no key
has been pressed within this span of time, an empty string is returned.
If the
timeout-argument is omitted, inkey$ will wait for ever.
Example
clear screen
open window 100,100
print "Press any key or press 'q' to stop."
repeat
a$=inkey$
print a$
until(a$="q")
This program simply returns the key pressed. You may use it, to learn, w
hich
strings are returned for the special keys on your keyboard (e.g.
function-keys).
See also
clear screen,mousex, mousey, mouseb, mousemod
------------------------------------------------------------------------
-------
Name
input ? read input from the user (or from a file) and assign it to a var
iable
Synopsis
input a
input a,b,c
input a$
input "Hello" a
input #1 a$
Description
input reads the new contents of one or many (numeric- or string-) variab
les,
either from the keyboard (i.e. from you) or from a file. An optional fir
st
string-argument specifies a prompt, which will be issued before reading
any
contents.
If you want to read from an open file, you need to specify a hash ('#'),
followed by the number, under which the file has been opened.
Note, that the input is split at spaces, i.e. if you enter a whole line
consisting of many space-separated word, the first input-statement will
only
return the first word; the other words will only be returned on subseque
nt
calls to input; the same applies, if a single input reads multiple varia
bles:
The first variable gets only the first word, the second one the second w
ord,
and so on. If you don't like this behaviour, you may use line input, whi
ch
returns a whole line (including embedded spaces) at once.
Example
input "Please enter the name of a file to read: " a$
open 1,a$
while(!eof(1))
input #1 b$
print b$
wend
If this program is stored within a file test.yab and you enter this name
when
prompted for a file to read, you will see this output:
Please enter the name of a file to read: t.yab
input
"Please
enter
the
name
of
a
file
to
read:
"
a$
open
1,a$
while(!eof(1))
input
#1
b$
print
b$
wend
See also
line input
------------------------------------------------------------------------
-------
Name
instr() ? searches its second argument within the first; returns its pos
ition
if found
Synopsis
print instr(a$,b$)
if (instr(a$,b$)) ?
pos=instr(a$,b$,x)
Description
The instr-functions requires two string arguments and searches the secon
d
argument within the first. If the second argument can be found within th
e
first, the position is returned (counting from one). If it can not be fo
und,
the instr-function returns 0; this makes this function usable within the
condition of an if-statement (see the example below).
If you supply a third, numeric argument to the instr-function, it will b
e used
as a starting point for the search. Therefore instr("abcdeabcdeabcde","e
",8)
will return 10, because the search for an "e" starts at position 8 and f
inds
the "e" at position 10 (and not the one at position 5).
Example
input "Please enter a text containing the string 'cat': " a$
if (instr(a$,"cat")) then
print "Well done !"
else
print "No cat in your input ..."
endif
See also
rinstr
------------------------------------------------------------------------
-------
Name
int() ? return the integer part of its single numeric argument
Synopsis
print int(a)
Description
The int-function returns only the digits before the comma; int(2.5) retu
rns 2
and int(-2.3) returns -2.
Example
input "Please enter a whole number between 1 and 10: " a
if (a=int(a) and a>=1 and a<=10) then
print "Thanx !"
else
print "Never mind ..."
endif
See also
frac, floor, ceil
L
label ? mark a specific location within your program for goto, gosub or
restore
left$() ? return (or change) left end of a string
len() ? return the length of a string
line ? draw a line
line input ? read in a whole line of text and assign it to a variable
local ? mark a variable as local to a subroutine
log() ? compute the natural logarithm
loop ? marks the end of an infinite loop
lower$() ? convert a string to lower case
ltrim$() ? trim spaces at the left end of a string
Name
label ? mark a specific location within your program for goto, gosub or
restore
Synopsis
label foo
?
goto foo
Description
The label-command can be used to give a name to a specific location with
in your
program. Such a position might be referred from one of three commands: g
oto,
gosub and restore.
You may use labels safely within libraries, because a label (e.g. foo) d
oes not
collide with a label with the same name within the main program or withi
n
another library; yabasic will not mix them up.
As an aside, please note, that line numbers are a special (however depre
cated)
case of labels; see the second example below.
Example
for a=1 to 100
if (ran(10)>5) goto done
next a
label done
10 for a=1 to 100
20 if (ran(10)>5) goto 40
30 next a
40
Within this example, the for-loop will probably be left prematurely with
a
goto-statement. This task is done twice: First with labels and then agai
n with
line numbers.
See also
gosub, goto.
------------------------------------------------------------------------
-------
Name
left$() ? return (or change) left end of a string
Synopsis
print left$(a$,2)
left$(b$,3)="foobar"
Description
The left$-function accepts two arguments (a string and a number) and ret
urns
the part from the left end of the string, whose length is specified by i
ts
second argument. Loosely spoken, it simply returns the requested number
of
chars from the left end of the given string.
Note, that the left$-function can be assigned to, i.e. it may appear on
the
left hand side of an assignment. In this way it is possible to change a
part of
the variable used within the left$-function. Note, that that way the len
gth of
the string cannot be changed, i.e. characters might be overwritten, but
not
added. For an example see below.
Example
input "Please answer yes or no: " a$
l=len(a$):a$=lower$(a$):print "Your answer is ";
if (left$("yes",l)=a$ and l>=1) then
print "yes"
elsif (left$("no",l)=a$ and l>=1) then
print "no"
else
print "?"
endif
This example asks a simple yes/no question and goes some way to accept e
ven
incomplete input, while still being able to reject invalid input.
This second example demonstrates the capability to assign to the
left$-function.
a$="Heiho World !"
print a$
left$(a$,5)="Hello"
print a$
See also
right$, mid$
------------------------------------------------------------------------
-------
Name
len() ? return the length of a string
Synopsis
x=len(a$)
Description
The len-function returns the length of its single string argument.
Example
input "Please enter a password: " a$
if (len(a$)<6) error "Password too short !"
This example checks the length of the password, that the user has entere
d.
See also
left$, right$ and mid$,
------------------------------------------------------------------------
-------
Name
line ? draw a line
Synopsis
open window 100,100
line 0,0,100,100
line 0,0 to 100,100
new curve
line 100,100
line to 100,100
open window 100,100
clear line 0,0,100,100
clear line 0,0 to 100,100
new curve
clear line 100,100
clear line to 100,100
Description
The line-command draws a line. Simple as this is, the line-command has a
large
variety of forms as they are listed in the synopsis above. Lets look at
them a
little closer:
* A line has a starting and an end point; therefore the line-command
(normally) needs four numbers as arguments, representing these two p
oints.
This is the first form appearing within the synopsis.
* You may separate the two points with either ',' or to, which account
s for
the second form of the line-command.
* The line-command may be used to draw a connected sequence of lines w
ith a
sequence of commands like line x,y; Each command will draw a line fr
om the
point where the last line-command left off, to the point specified i
n the
arguments. Note, that you need to use the command new curve before y
ou may
issue such a line-command. See the example below.
* You may insert the word to for beauty: line to x,y, which does exact
ly the
same as line x,y
* Finally, you may choose not to draw, but to erase the lines; this ca
n be
done by prepending the phrase clear. This account for all the other
forms
of the line-command.
Example
open window 200,200
line 10,10 to 10,190
line 10,190 to 190,190
new curve
for a=0 to 360
line to 10+a*180/360,100+60*sin(a*pi/180)
next a
This example draws a sine-curve (with an offset in x- and y-direction).
Note,
that the first line-command after new curve does not draw anything. Only
the
coordinates will be stored. The second iteration of the loop then uses t
hese
coordinates as a starting point for the first line.
See also
new curve, close curve, open window
------------------------------------------------------------------------
-------
Name
line input ? read in a whole line of text and assign it to a variable
Synopsis
line input a
line input a$
line input "Hello" a
line input #1 a$
Description
In most respects line input is like the input-command: It reads the new
contents of a variable, either from keyboard or from a file. However, li
ne
input always reads a complete line and assigns it to its variable. line
input
does not stop reading at spaces and is therefore the best way to read in
a
string which might contain whitespace. Note, that the final newline is s
tripped
of.
Example
line input "Please enter your name (e.g. Frodo Beutelin): " a$
print "Hello ",a$
Note that the usage of line input is essential in this example; a simple
input-statement would only return the string up to the first space, e.g.
Frodo.
See also
input
------------------------------------------------------------------------
-------
Name
local ? mark a variable as local to a subroutine
Synopsis
sub foo()
local a,b,c$,d(10),e$(5,5)
?
end sub
Description
The local-command can (and should be) used to mark a variable (or array)
as
local to the containing subroutine. This means, that a local variable in
your
subroutine is totally different from a variable with the same name withi
n your
main program. Variables which are known everywhere within your program a
re
called global in contrast.
Declaring variables within the subroutine as local helps to avoid hard t
o find
bugs; therefore local variables should be used whenever possible.
Note, that the parameters of your subroutines are always local.
As you may see from the example, local arrays may be created without usi
ng the
keyword dim (which is required only for global arrays).
Example
a=1
b=1
print a,b
foo()
print a,b
sub foo()
local a
a=2
b=2
end sub
This example demonstrates the difference between local and global variab
les; it
produces this output:
1 1
1 2
As you may see, the content of the global variable a is unchanged after
the
subroutine foo; this is because the assignment a=2 within the subroutine
affects the local variable a only and not the global one. However, the v
ariable
b is never declared local and therefore the subroutine changes the globa
l
variable, which is reflected in the output of the second print-statement
.
See also
sub, static, dim
------------------------------------------------------------------------
-------
Name
log() ? compute the natural logarithm
Synopsis
a=log(x)
a=log(x,base)
Description
The log-function computes the logarithm of its first argument. The optio
nal
second argument gives the base for the logarithm; if this second argumen
t is
omitted, the euler-constant 2.71828? will be taken as the base.
Example
open window 200,200
for x=10 to 190 step 10:for y=10 to 190 step 10
r=3*log(1+x,1+y)
if (r>10) r=10
if (r<1) r=1
fill circle x,y,r
next y:next x
This draws another nice plot.
See also
exp
------------------------------------------------------------------------
-------
Name
loop ? marks the end of an infinite loop
Synopsis
do
?
loop
Description
The loop-command marks the ends of a loop (which is started by do), wher
ein all
statements within the loop are repeated forever. In this respect the do
loop-loop is infinite, however, you may leave it anytime via break or go
to.
Example
print "Hello, I will throw dice, until I get a 2 ..."
do
r=int(ran(6))+1
print r
if (r=2) break
loop
See also
do, for, repeat, while, break
------------------------------------------------------------------------
-------
Name
lower$() ? convert a string to lower case
Synopsis
l$=lower$(a$)
Description
The lower$-function accepts a single string-argument and converts it to
all
lower case.
Example
input "Please enter a password: " a$
if (a$=lower$(a$)) error "Your password is NOT mixed case !"
This example prompts for a password and checks, if it is really lower ca
se.
See also
upper$
------------------------------------------------------------------------
-------
Name
ltrim$() ? trim spaces at the left end of a string
Synopsis
a$=ltrim$(b$)
Description
The ltrim$-function removes all whitespace from the left end of a string
and
returns the result.
Example
input "Please answer 'yes' or 'no' : " a$
a$=lower$(ltrim$(rtrim$(a$)))
if (len(a$)>0 and a$=left$("yes",len(a$))) then
print "Yes ..."
else
print "No ..."
endif
This example prompts for an answer and removes any spaces, which might p
recede
the input; therefore it is even prepared for the (albeit somewhat pathol
ogical
case, that the user first hits space before entering his answer.
See also
rtrim$, trim$
M
max() ? return the larger of its two arguments
mid$() ? return (or change) characters from within a string
min() ? return the smaller of its two arguments
mod ? compute the remainder of a division
mouseb ? extract the state of the mousebuttons from a string returned by
inkey$
mousemod ? return the state of the modifier keys during a mouseclick
mousex ? return the x-position of a mouseclick
mousey ? return the y-position of a mouseclick
Name
max() ? return the larger of its two arguments
Synopsis
print max(a,b)
Description
Return the maximum of its two arguments.
Example
dim m(10)
for a=1 to 1000
m=0
For b=1 to 10
m=max(m,ran(10))
next b
m(m)=m(m)+1
next a
for a=1 to 9
print a,": ",m(a)
next a
Within the inner for-loop (the one with the loop-variable b), the exampl
e
computes the maximum of 10 random numbers. The outer loop (with the loop
variable a) now repeats this process 1000 times and counts, how often ea
ch
maximum appears. The last loop finally reports the result.
Now, the interesting question would be, which will be approached, when w
e
increase the number of iterations from thousand to infinity. Well, maybe
someone could just tell me :-)
See also
min
------------------------------------------------------------------------
-------
Name
mid$() ? return (or change) characters from within a string
Synopsis
print mid$(a$,2,1)
print mid$(a$,2)
mid$(a$,5,3)="foo"
mid$(a$,5)="foo"
Description
The mid$-function requires three arguments: a string and two numbers, wh
ere the
first number specifies a position within the string and the second one g
ives
the number of characters to be returned; if you omit the second argument
, the
mid$-function returns all characters up to the end of the string.
Note, that you may assign to the mid$-function, i.e. mid$ may appear on
the
left hand side of an assignment. In this way it is possible to change a
part of
the variable used within the mid$-function. Note, that that way the leng
th of
the string cannot be changed, i.e. characters might be overwritten, but
not
added. For an example see below.
Example
input "Please enter a string: " a$
for a=1 to len(a$)
if (instr("aeiou",lower$(mid$(a$,a,1)))) mid$(a$,a,1)="e"
next a
print "When you turn everything to lower case and"
print "replace every vowel with 'e', your input reads:"
print
print a$
This example transforms the input string a bit, using the mid$-function
to
retrieve a character from within the string as well as to change it.
See also
left$ and right$.
------------------------------------------------------------------------
-------
Name
min() ? return the smaller of its two arguments
Synopsis
print min(a,b)
Description
Return the minimum of its two argument.
Example
dim m(10)
for a=1 to 1000
m=min(ran(10),ran(10))
m(m)=m(m)+1
next a
for a=1 to 9
print a,": ",m(a)
next a
For each iteration of the loop, the lower of two random number is record
ed. The
result is printed at the end.
See also
max
------------------------------------------------------------------------
-------
Name
mod ? compute the remainder of a division
Synopsis
print mod(a,b)
Description
The mod-function divides its two arguments and computes the remainder. N
ote,
that a/b-int(a/b) and mod(a,b) are always equal.
Example
clear screen
print at(10,10) "Please wait ";
p$="-\|/"
for a=1 to 100
rem ... do something lengthy here, or simply sleep :-)
pause(1)
print at(22,10) mid$(p$,1+mod(a,4))
next a
This example executes some time consuming action within a loop (in fact,
it
simply sleeps) and gives the user some indication of progress by display
ing a
turning bar (that's where the mod-function comes into play).
See also
int, frac
------------------------------------------------------------------------
-------
Name
mouseb ? extract the state of the mousebuttons from a string returned by
inkey$
Synopsis
inkey$
print mouseb()
print mouseb
a$=inkey$
print mouseb(a$)
Description
The mouseb-function is a helper function for decoding part of the (rathe
r
complicated) strings, which are returned by the inkey$-function. If a
mousebutton has been pressed, the mouseb-function returns the number (1,
2 or 3)
of the mousebutton, when it is pressed and returns its negative (-1,-2 o
r -3),
when it is released.
The mouseb-function accepts zero or one arguments. A single argument sho
uld be
a string returned by the inkey$-function; if mouseb is called without an
y
arguments, it returns the values from the last call to inkey$, which are
stored
implicitly and internally by yabasic.
Note
Note however, that the value returned by the mouseb-function does not re
flect
the current state of the mousebuttons. It rather extracts the informatio
n from
the string passed as an argument (or from the last call to the inkey$-fu
nction,
if no argument is passed). So the value returned by mouseb reflects the
state
of the mousebuttons at the time the inkey$-function has been called; as
opposed
to the time the mouseb-function is called.
Example
open window 200,200
clear screen
print "Please draw lines; press (and keep it pressed)"
print "the left mousebutton for the starting point,"
print "release it for the end-point."
do
if (mouseb(release$)=1) press$=release$
release$=inkey$
if (mouseb(release$)=-1) then
line mousex(press$),mousey(press$) to mousex(release$),mousey(releas
e$)
endif
loop
This is a maybe the most simplistic line-drawing program possible, catch
ing
presses as well as releases of the first mousebutton.
See also
inkey$, mousex, mousey and mousemod
------------------------------------------------------------------------
-------
Name
mousemod ? return the state of the modifier keys during a mouseclick
Synopsis
inkey$
print mousemod()
print mousemod
a$=inkey$
print mousemod(a$)
Description
The mousemod-function is a helper function for decoding part of the (rat
her
complicated) strings, which are returned by the inkey$-function if a
mousebutton has been pressed. It returns the state of the keyboard modif
iers
(shift, ctrl or alt): If the shift-key is pressed, mousemod returns 1, f
or the
alt-key 2 and for the ctrl-key 4. If more than one key is pressed, the s
um of
these values is returned, e.g. mousemod returns 5, if shift and ctrl are
pressed simultaneously.
The mousemod-function accepts zero or one arguments. A single argument s
hould
be a string returned by the inkey$-function; if mousemod is called witho
ut any
arguments, it returns the values from the last call to inkey$ (which are
stored
implicitly and internally by yabasic).
Note
Please see also the Note within the mouseb-function.
Example
open window 200,200
clear screen
do
a$=inkey$
if (left$(a$,2)="MB") then
x=mousex(a$)
y=mousey(a$)
if (mousemod(a$)=0) then
circle x,y,20
else
fill circle x,y,20
endif
endif
loop
This program draws a circle, whenever a mousebutton is pressed; the circ
les are
filled, when any modifier is pressed, and empty if not.
See also
inkey$, mousex, mousey and mouseb
------------------------------------------------------------------------
-------
Name
mousex ? return the x-position of a mouseclick
Synopsis
inkey$
print mousex()
print mousex
a$=inkey$
print mousex(a$)
Description
The mousex-function is a helper function for decoding part of the (rathe
r
complicated) strings, which are returned by the inkey$-function; It retu
rns the
x-position of the mouse as encoded within its argument.
The mousex-function accepts zero or one arguments. A single argument sho
uld be
a string returned by the inkey$-function; if mousex is called without an
y
arguments, it returns the values from the last call to inkey$ (which are
stored
implicitly and internally by yabasic).
Note
Please see also the Note within the mouseb-function.
Example
open window 200,200
clear screen
do
a$=inkey$
if (left$(a$,2)="MB") then
line mousex,0 to mousex,200
endif
loop
This example draws vertical lines at the position, where the mousebutton
has
been pressed.
See also
inkey$, mousemod, mousey and mouseb
------------------------------------------------------------------------
-------
Name
mousey ? return the y-position of a mouseclick
Synopsis
inkey$
print mousey()
print mousey
a$=inkey$
print mousey(a$)
Description
The mousey-function is a helper function for decoding part of the (rathe
r
complicated) strings, which are returned by the inkey$-function. mousey
returns
the y-position of the mouse as encoded within its argument.
The mousey-function accepts zero or one arguments. A single argument sho
uld be
a string returned by the inkey$-function; if mousey is called without an
y
arguments, it returns the values from the last call to inkey$ (which are
stored
implicitly and internally by yabasic).
Note
Please see also the Note within the mouseb-function.
Example
open window 200,200
clear screen
do
a$=inkey$
if (left$(a$,2)="MB") then
line 0,mousey to 200,mousey
endif
loop
This example draws horizontal lines at the position, where the mousebutt
on has
been pressed.
See also
inkey$, mousemod, mousex and mouseb
N
new curve ? start a new curve, that will be drawn with the line-command
next ? mark the end of a for loop
not ? negate an expression; can be written as !
numparams ? return the number of parameters, that have been passed to a
subroutine
Name
new curve ? start a new curve, that will be drawn with the line-command
Synopsis
new curve
line to x,y
Description
The new curve-function starts a new sequence of lines, that will be draw
n by
repeated line to-commands.
Example
open window 200,200
ellipse(100,50,30,60)
ellipse(150,100,60,30)
sub ellipse(x,y,xr,yr)
new curve
for a=0 to 2*pi step 0.2
line to x+xr*cos(a),y+yr*sin(a)
next a
close curve
end sub
This example defines a subroutine ellipse that draws an ellipse. Within
this
subroutine, the ellipse is drawn as a sequence of lines started with the
new
curve command and closed with close curve.
See also
line, close curve
------------------------------------------------------------------------
-------
Name
next ? mark the end of a for loop
Synopsis
for a=1 to 10
next a
Description
The next-keyword marks the end of a for-loop. All statements up to the
next-keyword will be repeated as specified with the for-clause. Note, th
at the
name of the variable is optional; so instead of next a you may write nex
t.
Example
for a=1 to 300000
for b=1 to 21+20*sin(pi*a/20)
print "*";
next b
print
sleep 0.1
next a
This example simply plots a sine-curve until you fall asleep.
See also
for
------------------------------------------------------------------------
-------
Name
not ? negate an expression; can be written as !
Synopsis
if (not a<b) then ?
bad=!okay
Description
The keyword not (or ! for short) is mostly used within conditions (e.g.
within
if- or while-statements). There it is employed to negate the condition o
r
expression (i.e. turn TRUE into FALSE and vice versa)
However not can be used within arithmetic calculations too., simply beca
use
there is no difference between arithmetic and logical expressions.
Example
input "Please enter three ascending numbers: " a,b,c
if (not (a<b and b<c)) error " the numbers you have entered are not asce
nding ..."
See also
and,or
------------------------------------------------------------------------
-------
Name
numparams ? return the number of parameters, that have been passed to a
subroutine
Synopsis
sub foo(a,b,c)
if (numparams=1) ?
?
end sub
Description
Within a subroutine the local variable numparam or numparams contains th
e
number of parameters, that have been passed to the subroutine. This info
rmation
can be useful, because the subroutine may have been called with fewer
parameters than actually declared. The number of values that actually ha
ve been
passed while calling the subroutine, can be found in numparams.
Note, that arguments which are used in the definition of a subroutine bu
t are
left out during a call to it (thereby reducing the value of numparams) r
eceive
a value of 0 or "" (empty string) respectively.
Example
a$="123456789"
print part$(a$,4)
print part$(a$,3,7)
sub part$(a$,f,t)
if (numparams=2) then
return mid$(a$,f)
else
return mid$(a$,f,t-f+1)
end if
end sub
When you run this example, it will print 456789 and 34567. Take a look a
t the
subroutine part$, which returns part of the string which has been passed
as an
argument. If (besides the string) two numbers are passed, they define th
e
starting and end position of the substring, that will be returned. Howev
er, if
only one number is passed, the rest of the string, starting from this po
sition
will be returned. Each of these cases is recognized with the help of the
numparams variable.
See also
sub
O
on gosub ? jump to one of multiple gosub-targets
on goto ? jump to one of many goto-targets
on interrupt ? change reaction on keyboard interrupts
open ? open a file
open printer ? open printer for printing graphics
open window ? open a graphic window
logical or ? logical or, used in conditions
or() ? arithmetic or, used for bit-operations
Name
on goto ? jump to one of multiple gosub-targets
Synopsis
on a gosub foo,bar,baz
?
label foo
?
return
label bar
?
return
label baz
?
return
Description
The on gosub statement uses its numeric argument (the one between on and
gosub)
to select an element from the list of labels, which follows after the
gosub-keyword: If the number is 1, the program does a gosub to the first
label;
if the number is 2, to the second and, so on. if the number is zero or l
ess,
the program continues at the position of the first label; if the number
is
larger than the total count of labels, the execution continues at the po
sition
of the last label; i.e. the first and last label in the list constitute
some
kind of fallback-slot.
Note, that the on gosub-command can no longer be considered state of the
art;
people (not me !) may even start to mock you, if you use it.
Example
do
print "Please enter a number between 1 and 3: "
print
input "Your choice " a
on a gosub bad,one,two,three,bad
loop
label bad
print "No. Please between 1 and 3"
return
label one
print "one"
return
label two
print "two"
return
label three
print "three"
return
Note, how invalid input (a number less than 1, or larger than 3) is
automatically detected.
See also
goto, on gosub/function>
------------------------------------------------------------------------
-------
Name
on goto ? jump to one of many goto-targets
Synopsis
on a goto foo,bar,baz
?
label foo
?
label bar
?
label baz
?
Description
The on goto statement uses its numeric argument (the one between on and
goto to
select an element from the list of labels, which follows after the
goto-keyword: If the number is 1, the execution continues at the first l
abel;
if the number is 2, at the second, and so on. if the number is zero or l
ess,
the program continues at the position of the first label; if the number
is
larger than the total count of labels, the execution continues at the po
sition
of the last label; i.e. the first and last label in the list constitute
some
kind of fallback-slot.
Note, that (unlike the goto-command) the on goto-command can no longer b
e
considered state of the art; people may (not me !) even start to mock yo
u, if
you use it.
Example
label over
print "Please Select one of these choices: "
print
print " 1 -- show time"
print " 2 -- show date"
print " 3 -- exit"
print
input "Your choice " a
on a goto over,show_time,show_date,terminate,over
label show_time
print time$()
goto over
label show_date
print date$()
goto over
label terminate
exit
Note, how invalid input (a number less than 1, or larger than 3) is
automatically detected; in such a case the question is simply issued aga
in.
See also
goto, on gosub/function>
------------------------------------------------------------------------
-------
Name
on interrupt ? change reaction on keyboard interrupts
Synopsis
on interrupt break
?
on interrupt continue
Description
With the on interrupt-command you may change the way, how yabasic reacts
on a
keyboard interrupt; it comes in two variants: on interrupt break and on
interrupt continue. A keyboard interrupt is produced, if you press ctrl-
C on
your keyboard; normally (and certainly after you have called on interrup
t
break), yabasic will terminate with an error message. However after the
command
on interrupt continue yabasic ignores any keyboard interrupt. This may b
e
useful, if you do not want your program being interruptible during certa
in
critical operations (e.g. updating of files).
Example
print "Please stand by while writing a file with random data ..."
on interrupt continue
open "random.data" for writing as #1
for a=1 to 100
print #1 ran(100)
print a," percent done."
sleep 1
next a
close #1
on interrupt continue
This program writes a file with 100 random numbers. The on interrupt con
tinue
command insures, that the program will not be terminated on a keyboard
interrupt and the file will be written entirely in any case. The sleep-c
ommand
just stretches the process artificially to give you a chance to try a ct
rl-C.
See also
There is no related command.
------------------------------------------------------------------------
-------
Name
open ? open a file
Synopsis
open a,"file","r"
open #a,"file","w"
open #a,printer
open "file" for reading as a
open "file" for writing as #a
a=open("file")
a=open("file","r")
if (open(a,"file")) ?
if (open(a,"file","w")) ?
Description
The open-command opens a file for reading or writing or a printer for pr
inting
text. open comes in a wide variety of ways; it requires these arguments:
filenumber
In the synopsis this is a or #a. In yabasic each file is associated
with a
number between 1 and a maximum value, which depends on the operating
system. For historical reasons the filenumber can be preceded by a h
ash ('#
'). Note, that specifying a filenumber is optional; if it is omitted
, the
open-function will return a filenumber, which should then be stored
in a
variable for later reference. This filenumber can be a simple number
or an
arbitrary complex arithmetic expression, in which case braces might
be
necessary to save yabasic from getting confused.
filename
In the synopsis above this is "file". This string specifies the name
of the
file to open (note the important caveat on specifying these filename
s).
accessmode
In the synopsis this is "r", "w", for reading or for writing. This s
tring
or clause specifies the mode in which the file is opened; it may be
one of:
"r"
Open the file for reading (may also be written as for reading).
If the
file does not exist, the command will fail. This mode is the def
ault,
i.e. if no mode is specified with the open-command, the file wil
l be
opened with this mode.
"w"
Open the file for writing (may also be written as for writing).
If the
file does not exist, it will be created.
"a"
Open the file for appending, i.e. what you write to the file wil
l be
appended after its initial contents. If the file does not exist,
it
will be created.
"b"
This letter may not appear alone, but may be combined with the o
ther
letters (e.g. "rb") to open a file in binary mode (as opposed to
text
mode).
As you may see from the synopsis, the open-command may either be called
as a
command (without braces) or as a function (with braces). If called as a
function, it will return the filenumber or zero if the operation fails.
Therefore the open-function may be used within the condition of an
if-statement.
If the open-command fails, you may use peek("error") to retrieve the exa
ct
nature of the error.
Furthermore note, that there is another, somewhat separate usage of the
open-command; if you specify the bareword printer instead of a filename,
the
command opens a printer for printing text. Every text (and only text) yo
u print
to this file will appear on your printer. Note, that this is very differ
ent
from printing graphics, as can be done with open printer.
Example
open "foo.bar" for writing as #1
print #1 "Hallo !"
close #1
if (not open(1,"foo.bar")) error "Could not open 'foo.bar' for reading"
while(not eof(1))
line input #1 a$
print a$
wend
This example simply opens the file foo.bar, writes a single line, reopen
s it
and reads its contents again.
See also
close, print, peek, peek("error") and open printer
------------------------------------------------------------------------
-------
Name
open printer ? open printer for printing graphics
Synopsis
open printer
open printer "file"
Description
The open printer-command opens a printer for printing graphics. The comm
and
requires, that a graphic window has been opened before. Everything that
is
drawn into this window will then be sent to the printer too.
A new piece of paper may be started with the clear window-command; the f
inal
(or only) page will appear after the close printer-command.
Note, that you may specify a filename with open printer; in that case th
e
printout will be sent to a filename instead to a printer. Your program o
r the
user will be responsible for sending this file to the printer afterwards
.
If you use yabasic under Unix, you will need a postscript printer (becau
se
yabasic produces postscript output). Alternatively you may use ghostscri
pt to
transform the postscript file into a form suitable for your printer; but
that
is beyond the responsibility of yabasic.
Example
open window 200,200
open printer
line 0,0 to 200,200
text 100,100,"Hallo"
close window
close printer
This example will open a window, draw a line and print some text within;
everything will appear on your printer too.
See also
close printer
------------------------------------------------------------------------
-------
Name
open window ? open a graphic window
Synopsis
open window x,y
open window x,y,"font"
Description
The open window-command opens a window of the specified size. Only one w
indow
can be opened at any given moment of time.
An optional third argument specifies a font to be used for any text with
in the
window. It can however be changed with any subsequent text-command.
Example
for a=200 to 400 step 10
open window a,a
for b=0 to a
line 0,b to a,b
line b,0 to b,a
sleep 0.1
close window
next a
See also
close window, text
------------------------------------------------------------------------
-------
Name
or ? logical or, used in conditions
Synopsis
if (a or b) ?
while (a or b) ?
Description
Used in conditions (e.g within if or while) to join two expressions. Ret
urns
true, if either its left or its right or both arguments are true; return
s false
otherwise.
Example
input "Please enter a number"
if (a>9 or a<1) print "a is not between 1 and 9"
See also
and,not
------------------------------------------------------------------------
-------
Name
or() ? arithmetic or, used for bit-operations
Synopsis
x=or(a,b)
Description
Used to compute the bitwise or of both its argument. Both arguments are
treated
as binary numbers (i.e. a series of 0 and 1); a bit of the resulting val
ue will
then be 1, if any of its arguments has 1 at this position in their binar
y
representation.
Note, that both arguments are silently converted to integer values and t
hat
negative numbers have their own binary representation and may lead to
unexpected results when passed to or.
Example
print or(14,3)
This will print 15. This result is clear, if you note, that the binary
representation of 14 and 3 are 1110 and 0011 respectively; this will yie
ld 1111
in binary representation or 15 as decimal.
See also
oand, eor and not
P
pause ? pause, sleep, wait for the specified number of seconds
peek ? retrieve various internal information
peek$ ? retrieve various internal string-information
pi ? a constant with the value 3.14159
poke ? change selected internals of yabasic
print ? Write to terminal or file
print color ? print with color
print colour ? see print color
putbit ? draw a rectangle of pixels encoded within a string into the gra
phics
window
putscreen ? draw a rectangle of characters into the text terminal
Name
pause ? pause, sleep, wait for the specified number of seconds
Synopsis
pause 5
Description
The pause-command has many different names: You may write pause, sleep o
r wait
interchangeably; whatever you write, yabasic will always do exactly the
same.
The pause-command will simply wait for the specified number of seconds.
This
may be a fractional number, so you may well wait less than a second. How
ever,
if you try to pause for a smaller and smaller interval (e.g. 0.1 seconds
, 0.01
seconds, 0.001 seconds and so on) you will find that at some point yabas
ic will
not wait at all. The minimal interval that can be waited depends on the
system
(Unix, Windows) you are using.
The pause-command cannot be interrupted. However, sometimes you may want
the
wait to be interruptible by simply pressing a key on the keyboard. In su
ch
cases you should consider using the inkey$-function, with a number of se
conds
as an argument).
Example
deg=0
do
maxx=44+40*sin(deg)
for x=1 to maxx
print "*";
next x
pause 0.1+(maxx*maxx/(4*84*84))
print
deg=deg+0.1
loop
This example draws a sine-curve; due to the pause-statement the speed of
drawing varies in the same way as the speed of a ball might vary, if it
would
roll along this curve under the influence of gravity.
See also
sleep, wait
------------------------------------------------------------------------
-------
Name
peek ? retrieve various internal information
Synopsis
print peek("foo")
a=peek(#1)
Description
The peek-function has many different and mostly unrelated uses. It is a
kind of
grab-bag for retrieving all kinds of numerical information, internal to
yabasic
. The meaning of the numbers returned be the peek-function depends on th
e
string or number passed as an argument.
peek always returns a number, however the closely related peek$-function
exists, which may be used to retrieve string information from among the
internals of yabasic. Finally note, that some of the values which are re
trieved
with peek may even be changed, using the poke-function.
There are two variants of the peek-function: One expects an integer, pos
itive
number and is described within the first entry of the list below. The ot
her
variant expects one of a well defined set of strings as described in the
second
and all the following entries of the list below.
peek(a)
Read a single character from the file a (which must be open of cours
e).
peek("argument")
Return the number of arguments, that have been passed to yabasic at
invocation time. E.g. if yabasic has been called like this: yabasic
foo.yab
bar baz, then peek("argument") will return 2. This is because foo.ya
b is
treated as the name of the program to run, whereas bar and baz are
considered arguments to the program, which are passed on the command
line.
Note, that for windows-users, who tend to click on the icon (as oppo
sed to
starting yabasic on the command line), this peekwill mostly return 0
.
The function peek("argument") can be written as peek("arguments") to
o.
You will want to check out the corresponding function peek$("argumen
t") to
actually retrieve the arguments. Note, that each call to peek$("argu
ment")
reduces the number returned by peek("argument").
peek("error")
Return a number specifying the nature of the last error in an open-
or
seek-statement. Normally an error within an open-statement immediate
ly
terminates your program with an appropriate error-message, so there
is no
chance and no need to learn more about the nature of the error. Howe
ver, if
you use open as a condition (e.g. if (open(#1,"foo")) ?) the outcome
(success or failure) of the open-operation will determine, if the co
ndition
evaluates to true or false. If now such an operation fails, your pro
gram
will not be terminated and you might want to learn the reason for fa
ilure.
This reason will be returned by peek("error") (as a number) or by pe
ek$
("error") (as a string)
The table below shows the various error codes; the value returned by
peek$
("error") explains the nature of the error. Note, that the codes 10,
11 and
12 refer to the seek-command.
Table 7.1. Error codes
+-------------------------------------------------------------------
------+
| peek |peek$("error")| Explanation
|
|("error")| |
|
|---------+--------------+------------------------------------------
------|
| 2 |Stream already|Do not try to open one and the same filenu
mber |
| |in use |twice; rather close it first.
|
|---------+--------------+------------------------------------------
------|
| |'x' is not a |The optional filemode argument, which may
be |
| 3 |valid filemode|passed to the open-function, has an invali
d |
| | |value
|
|---------+--------------+------------------------------------------
------|
| 4 |could not open|The open-call did not work, no further
|
| |'foo' |explanation is available.
|
|---------+--------------+------------------------------------------
------|
| |reached |You have opened more files than your opera
ting |
| 5 |maximum number|system permits.
|
| |of open files |
|
|---------+--------------+------------------------------------------
------|
| |cannot open |The commands open printer and open #1,prin
ter |
| |printer: |both open a printer (refer to their descri
ption |
| 6 |already |for the difference). However, only one can
be |
| |printing |active at a time; if you try to do both at
the |
| |graphics |same time, you will receive this error.
|
|---------+--------------+------------------------------------------
------|
| 7 |could not open|Well, it simply did not work.
|
| |line printer |
|
|---------+--------------+------------------------------------------
------|
| 9 |invalid stream|An attempt to use an invalid (e.g. negativ
e) |
| |number |stream number; example: open(-1,"foo")
|
|---------+--------------+------------------------------------------
------|
| |could not |
|
| 10 |position |seek did not work.
|
| |stream x to |
|
| |byte y |
|
|---------+--------------+------------------------------------------
------|
| 11 |stream x not |You have tried to seek within a stream, th
at has|
| |open |not been opened yet.
|
|---------+--------------+------------------------------------------
------|
| |seek mode 'x' |The argument, which has been passed to see
k is |
| 12 |is none of |invalid.
|
| |begin,end,here|
|
+-------------------------------------------------------------------
------+
peek("fontheight")
Return the height of the font used within the graphic window. If non
e is
open, this peek will return the height of the last font used or 10,
if no
window has been opened yet.
peek("screenheight")
Return the height in characters of the window, wherein yabasic runs.
If you
have not called clear screen yet, this peekwill return 0, regardless
of the
size of your terminal.
peek("screenwidth")
Return the width in characters of the window, wherein yabasic runs.
If you
have not called clear screen yet, this peekwill return 0, regardless
of the
size of your terminal.
peek("secondsrunning")
Return the number of seconds that have passed since the start of yab
asic.
peek("millisrunning")
Return the number of milliseconds, that have passed since the start
of
yabasic.
peek("version")
Return the version number of yabasic, e.g. 2.77. See also the relate
d peek$
("version"), which returns nearly the same information (plus the
patchlevel) as a string, e.g. "2.77.1".
peek("winheight")
Return the height of the graphic-window in pixels. If none is open,
this
peek will return the height of the last window opened or 100, if non
e has
been opened yet.
peek("winwidth")
Return the width of the graphic-window in pixels. If none is open, t
his
peek will return the width of the last window opened or 100, if none
has
been opened yet.
peek("isbound")
Return true, if the executing yabasic-program is part of a standalon
e
program; see the section about creating a standalone-program for det
ails.
peek("version")
Return the version number of yabasic (e.g. 2.72).
Example
open "foo" for reading as #1
open "bar" for writing as #2
while(not eof(#1))
poke #2,chr$(peek(#1));
wend
This program will copy the file foo byte by byte to bar.
Note, that each peek does something entirely different, and only one has
been
demonstrated above. Therefore you need to make up examples yourself for
all the
other peeks.
See also
peek$, poke, open
------------------------------------------------------------------------
-------
Name
peek$ ? retrieve various internal string-information
Synopsis
print peek$("foo")
Description
The peek$-function has many different and unrelated uses. It is a kind o
f
grab-bag for retrieving all kinds of string information, internal to yab
asic;
the exact nature of the strings returned be the peek$-function depends o
n the
string passed as an argument.
peek$ always returns a string, however the closely related peek-function
exists, which may be used to retrieve numerical information from among t
he
internals of yabasic. Finally note, that some of the values which are re
trieved
with peek$ may even be changed, using the poke-function.
The following list shows all possible arguments to peek$:
peek$("infolevel")
Returns either "debug", "note", "warning", "error" or "fatal", depen
ding on
the current infolevel. This value can be specified with an option on
the
command line or changed during the execution of the program with the
corresponding poke; however, normally only the author of yabasic (me
!)
would want to change this from its default value "warning".
peek$("textalign")
Returns one of nine possible strings, specifying the default alignme
nt of
text within the graphics-window. The alignment-string returned by th
is peek
describes, how the text-command aligns its string-argument with resp
ect to
the coordinates supplied. However, this value does not apply, if the
text-command explicitly specifies an alignment. Each of these string
s is
two characters long. The first character specifies the horizontal al
ignment
and can be either l, r or c, which stand for left, right or center.
The
second character specifies the vertical alignment and can be one of
t, b or
c, which stand for top, bottom or center respectively.
You may change this value with the corresponding command poke
"textalign",?; the initial value is lb, which means the top of the l
eft and
the top edge if the text will be aligned with the coordinates, that
are
specified within the text-command.
peek$("windoworigin")
This peek returns a two character string, which specifies the positi
on of
the origin of the coordinate system of the window; this string might
be
changed with the corresponding command poke "windoworigin",x,y or sp
ecified
as the argument of the origin command; see there for a detailed desc
ription
of the string, which might be returned by this peek.
peek$("program_name")
Returns the name of the yabasic-program that is currently executing;
typically this is the name, that you have specified on the commandli
ne, but
without any path-components. So this peek$ might return foo.yab. As
a
special case when yabasic has been invoked without the name of a pro
gram to
be executed this peek will return the literal strings standard input
or,
when also the option -e has been specified, command line. See also p
eek$
("program_file_name") and peek$("interpreter_path") for related
information.
peek$("program_file_name")
Returns the full file-name of the yabasic-program that is currently
executing; typically this is the name, that you have specified on th
e
commandline, including any path-components. For the special case, th
at you
have bound your yabasic-program with the interpreter to a single sta
ndalone
executable, this peek$ will return its name. See also peek$("program
_name")
and peek$("interpreter_path") for related information.
peek$("interpreter_path")
Return the full file-name of the yabasic-interpreter that is current
ly
executing your program; typically this will end on yabasic or yabasi
c.exe
depending on your platform and the path will be where you installed
yabasic
. For bound programs (see creating a standalone-program) however, th
is may
be different and will include whatever you specified during the bind
-command.
See also peek$("program_name") and peek$("program_file_name") for re
lated
information. Employing these, it would be possible for a yabasic-pro
gram to
start itself: system(peek$("interpreter_path") + " " + peek$
("program_file_name")). Of course, in this simple form this would be
a bad
idea, because this would start concurrent instances of yabasic witho
ut end.
peek$("error")
Return a string describing the nature of the last error in an open-
or
seek-statement. See the corresponding peek("error") for a detailed
description.
peek$("library")
Return the name of the library, this statement is contained in. See
the
import-command for a detailed description or for more about librarie
s.
peek$("version")
Version of yabasic as a string; e.g. 2.77.1. See also the related pe
ek
("version"), which returns nearly the same information (minus the
patchlevel) as a number, e.g. 2.77.
peek$("os")
This peek returns the name of the operating system, where your progr
am
executes. This can be either windows or unix.
peek$("font")
Return the name of the font, which is used for text within the graph
ic
window; this value can be specified as the third argument to the ope
n
window-command.
peek$("env","NAME")
Return the environment variable specified by NAME (which may be any
string
expression). Which kind of environment variables are available on yo
ur
system depends, as well as their meaning, on your system; however ty
ping
env on the command line will produce a list (for Windows and Unix al
ike).
Note, that peek$("env",...) can be written as peek$("environment",..
.) too.
peek$("argument")
Return one of the arguments, that have been passed to yabasic at inv
ocation
time (the next call will return the the second argument, and so on).
E.g.
if yabasic has been called like this: yabasic foo.yab bar baz, then
the
first call to peek$("argument") will return bar. This is because foo
.yab is
treated as the name of the program to run, whereas bar and baz are
considered arguments to this program, which are passed on the comman
d line.
The second call to peek$("argument") will return baz. Note, that for
windows-users, who tend to click on the icon (as opposed to starting
yabasic on the command line), this peekwill mostly return the empty
string.
Note, that peek$("argument") can be written as peek$("arguments").
Finally you will want to check out the corresponding function peek
("argument").
Example
print "You have supplied these arguments: "
while(peek("argument"))
print peek("argument"),peek$("argument")
wend
If you save this program in a file foo.yab and execute it via yabasic t.
yab a b
c (for windows users: please use the command line for this), your will g
et this
output:
3a
2b
1c
See also
peek, poke, open
------------------------------------------------------------------------
-------
Name
pi ? a constant with the value 3.14159
Synopsis
print pi
Description
pi is 3.14159265359 (well at least for yabasic); do not try to assign to
pi
(e.g. pi=22/7) this would not only be mathematically dubious, but would
also
result in a syntax error.
Example
for a=0 to 180
print "The sine of ",a," degrees is ",sin(a*pi/180)
next a
This program uses pi to transform an angle from degrees into radians.
See also
euler
------------------------------------------------------------------------
-------
Name
poke ? change selected internals of yabasic
Synopsis
poke "foo","bar"
poke "foo",baz
poke #a,"bar"
poke #a,baz
Description
The poke-command may be used to change details of yabasic's behaviour. L
ike the
related function peek, poke does many different things, depending on the
arguments supplied.
Here are the different things you can do with poke:
poke 5,a
Write the given byte (a in the example above) to the specified strea
m (5#a
in the example).
See also the related function function peek(1).
poke "dump","filename.dump"
Dump the internal form of your basic-program to the named file; this
is
only useful for debugging the internals of yabasic itself.
The second argument ("filename.dump" in the example) should be the n
ame of
a file, that gets overwritten with the dump, please be careful.
poke "fontheight",12
This poke changes the default fontheight. This can only have an effe
ct, if
the fonts given in the commands text or open window do not specify a
fontheight on their own.
poke "font","fontname"
This poke specifies the default font. This can only have an effect,
if you
do not supply a fontname with the commands text or open window.
poke "infolevel","debug"
Change the amount of internal information, that yabasic outputs duri
ng
execution.
The second argument can be either "debug", "note", "warning", "error
" or
"fatal". However, normally you will not want to change this from its
default value "warning".
See also the related peek$("infolevel").
poke "random_seed",42
Set the seed for the random number generator; if you do this, the ra
n
-function will return the same sequence of numbers every time the pr
ogram
is started.
poke "stdout","some text"
Send the given text to standard output. Normally one would use print
for
this purpose; however, sending e.g. control characters to your termi
nal is
easier with this poke.
poke "textalign","cc"
This poke changes the default alignment of text with respect to the
coordinates supplied within the text-command. However, this value do
es not
apply, if the text-command explicitly specifies an alignment. The se
cond
argument ("cc" in the example) must always be two characters long; t
he
first character can be one of l (left), r (right) or c (center); the
second
character can be either t (top), b (bottom) or c (center); see the
corresponding peek$("textalign") for a detailed description of this
argument.
poke "windoworigin","lt"
This poke moves the origin of the coordinate system of the window to
the
specified position. The second argument ("lt" in the example) must a
lways
be two characters long; the first character can be one of l (left),
r (
right) or c (center); the second character can be either t (top), b
(bottom
) or c (center). Together those two characters specify the new posit
ion of
the coordinate-origin. See the corresponding peek$("windoworigin") f
or a
more in depth description of this argument.
Example
print "Hello, now you will see, how much work"
print "a simple for-loop involves ..."
input "Please press return " a$
poke "infolevel","debug"
for a=1 to 10:next a
This example only demonstrates one of the many pokes, which are describe
d
above: The program switches the infolevel to debug, which makes yabasic
produce
a lot of debug-messages during the subsequent for-loop.
See also
peek, peek$
------------------------------------------------------------------------
-------
Name
print ? Write to terminal or file
Synopsis
print "foo",a$,b
print "foo",a$,b;
print #a "foo",a$
print #a "foo",a$;
print foo using "##.###"
print reverse "foo"
print at(10,10) a$,b
print @(10,10) a$,b
print color("red","blue") a$,b
print color("magenta") a$,b
print color("green","yellow") at(5,5) a$,b
Description
The print-statement outputs strings or characters, either to your termin
al
(also known as console) or to an open file.
To understand all those uses of the print-statement, let's go through th
e
various lines in the synopsis above:
print "foo",a$,b
Print the string foo as well as the contents of the variables a$ and
b onto
the screen, silently adding a newline.
print "foo",a$,b;
(Note the trailing semicolon !) This statement does the same as the
one
above; only the implicit newline is skipped, which means that the ne
xt
print-statement will append seamlessly.
print #a "foo",a$
This is the way to write to files. The file with the number a must b
e open
already, an implicit newline is added. Note the file-number #a, whic
h
starts with a hash ('#') amd is separated from the rest of the state
ment by
a space only. The file-number (contained in the variable a) must hav
e been
returned by a previous open-statement (e.g. a=open("bar")).
print #a "foo",a$;
The same as above, but without the implicit newline.
print foo using "##.###"
Print the number foo with as many digits before and after the decima
l dot
as given by the number of '#'-signs. See the entries for using and s
tr$ for
a detailed description of this format.
print reverse "foo"
As all the print-variants to follow, this form of the print-statemen
t can
only be issued after clear screen has been called. The strings and n
umbers
after the reverse-clause are simply printed inverse (compared to the
normal
print-statement).
print at(10,10) a$,b
Print at the specified (x,y)-position. This is only allowed after cl
ear
screen has been called. You may want to query peek$("screenwidth") o
r peek$
("screenheight") to learn the actual size of your screen. You may ad
d a
semicolon to suppress the implicit newline.
print @(10,10) a$,b
This is exactly the same as above, however, at may be written as @.
print color("red","blue") at(5,5) a$,b
Print with the specified fore- ("red") and background ("blue") color
(or
colour). The possible values are "black", "white", "red", "blue", "g
reen",
"yellow", "cyan" or "magenta". Again, you need to call clear screen
first
and add a semicolon if you want to suppress the implicit newline.
print color("magenta") a$,b
You may specify the foreground color only.
print color("green","yellow") a$,b
A color and a position (in this sequence, not the other way around)
may be
specified at once.
Example
clear screen
columns=peek("screenwidth")
lines=peek("screenheight")
dim col$(7)
for a=0 to 7:read col$(a):next a
data "black","white","red","blue","green","yellow","cyan","magenta"
for a=0 to 2*pi step 0.1
print colour(col$(mod(i,8))) at(columns*(0.8*sin(a)+0.9)/2,lines*(0.8*
cos(a)+0.9)/2) "*"
i=i+1
next a
This example draws a colored ellipse within the text window.
See also
at, print color, input, clear screen, using, ;
------------------------------------------------------------------------
-------
Name
print color ? print with color
Synopsis
print color(fore$) text$
print color(fore$,back$) text$
Description
Not a separate command, but part of the print-command; may be included j
ust
after print and can only be issued after clear screen has been executed.
color() takes one or two string-arguments, specifying the color of the t
ext and
(optionally) the background.
The one or two strings passed to color() can be one of these: "black", "
white",
"red", "blue", "green", "yellow", "cyan" and "magenta" (which can be
abbreviated as "bla", "whi", "red", "blu", "gre", "yel", "cya" and "mag"
respectively).
color() can only be used, if clear scren has been issued at least once.
Note, that color() can be written as colour() too.
Example
clear screen
dim col$(7):for a=0 to 7:read col$(a):next a
do
print color(col$(ran(7)),col$(ran(7))) " Hallo ";
pause 0.01
loop
data "black","white","red","blue"
data "green","yellow","cyan","magenta"
This prints the word " Hallo " in all colors across your screen.
See also
print, clear screen, at
------------------------------------------------------------------------
-------
Name
print colour ? see print color
Synopsis
print colour(fore$) text$
print colour(fore$,back$) text$
See also
color
------------------------------------------------------------------------
-------
Name
putbit ? draw a rectangle of pixels encoded within a string into the gra
phics
window
Synopsis
open window 200,200
?
a$=getbit(20,20,50,50)
?
putbit a$,30,30
putbit a$ to 30,30
putbit a$,30,30,"or"
Description
The putbit-command is the counterpart of the getbit$-function. putbit re
quires
a string as returned by the getbit-function. Such a string contains a re
ctangle
from the graphic window; the putbit-function puts such a rectangular reg
ion
back into the graphic-window.
Note, that the putbit-command currently accepts a fourth argument. Howev
er only
the string value "or" is supported here. The effect is, that only those
pixel,
which are set in the string will be set in the graphic window. Those pix
els,
which are not set in the string, will not change in the window (as oppos
ed to
being cleared).
Example
c$="rgb 21,21:0000000000000000000000000000000000000000000000000000000000
000032c8000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000032c80032c80032c80032c80032c80032c80032c80032c80032c800
00000000000000000000000000000000000000000000000000000000000032c80032c80032c80032
c80032c80032c80032c80032c80032c80032c80032c80032c8000000000000000000000000000000
0000000000000000000032c80032c80032c80032c80032c80032c80032c80032c80032c80032c800
32c80032c80032c80032c80032c80000000000000000000000000000000032c80032c80032c80032
c80032c80032c80032c80032c8c8ff000032c80032c80032c80032c80032c80032c80032c8000000
0000000000000000000000000032c80032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8
ff00c8ff00c8ff000032c80032c80032c80032c80032c80000000000000000000032c80032c80032
c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c8
0032c80032c80032c80000000000000032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8
ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80000000000000032
c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00
c8ff000032c80032c80032c80032c80000000000000032c80032c80032c80032c8c8ff00c8ff00c8
ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80000
000032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00
c8ff00c8ff00c8ff000032c80032c80032c80032c80000000000000032c80032c80032c80032c8c8
ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032
c80032c80000000000000032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00
c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80000000000000032c80032c800
32c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032
c80032c80032c80032c80000000000000032c80032c80032c80032c80032c8c8ff00c8ff00c8ff00
c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80032c800000000000000
00000032c80032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032
c80032c80032c80032c80032c80000000000000000000000000032c80032c80032c80032c80032c8
0032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032c800000000000000
00000000000000000000000032c80032c80032c80032c80032c80032c80032c80032c80032c80032
c80032c80032c80032c80032c80032c80000000000000000000000000000000000000000000032c8
0032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032c800000000000000
00000000000000000000000000000000000000000000000000000032c80032c80032c80032c80032
c80032c80032c80032c80032c8000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000"
open window 200,200
do
x=ran(220)-10
y=ran(220)-10
putbit c$,x,y,"transparent"
loop
This program uses a precanned string (containing the image of a blue cir
cle
with a yellow centre) and draws it repeatedly into the graphic-window. T
he mode
"transparent" ensures, that no pixels will be cleared.
There are two possible values for the third argument of putbit. Both mod
es
differ in the way, they replace (or not) any pixels from the window with
pixels
from the bitmap having the background colour.
transparent or t
With this mode the pixels from the window will be kept, if the bitma
p
contains pixels with background colour at this position; i.e. the bi
tmap is
transparent
solid or s
With this mode the pixels from the window will be overpainted with t
he
pixels from the bitmap in any case; i.e. the bitmap is solid
If you omit this argument, the default transparent applies.
See also
getbit$, open window
------------------------------------------------------------------------
-------
Name
putscreen ? draw a rectangle of characters into the text terminal
Synopsis
clear screen
?
a$=getscreen$(5,5,10,10)
?
putscreen a$,7,7
Description
The putscreen-command is the counterpart of the getscreen$-function. put
screen
requires a string as returned by the getscreen-function. Such a string c
ontains
a rectangular detail from the terminal; the putscreen-function puts such
a
region back into the terminal-window.
Note, that clear screen must have been called before.
Example
clear screen
for a=1 to 200
print color("red") "Hallo !";
print color("blue") "Welt !";
next a
r$=getscreen$(0,0,20,20)
for x=0 to 60
putscreen r$,x,0
sleep 0.1
next x
This example prints the string "Hallo !Welt !" all over the screen and t
hen
moves a rectangle from one side to the other.
See also
getscreen$, clear screen
R
ran() ? return a random number
read ? read data from data-statements
rectangle ? draw a rectangle
redim ? create an array prior to its first use. A synonym for dim
rem ? start a comment
repeat ? start a repeat-loop
restore ? reposition the data-pointer
return ? return from a subroutine or a gosub
reverse ? print reverse (background and foreground colors exchanged)
right$() ? return (or change) the right end of a string
rinstr() ? find the rightmost occurrence of one string within the other
rtrim$() ? trim spaces at the right end of a string
Name
ran() ? return a random number
Synopsis
print ran()
x=ran(y)
Description
The ran-function returns a random number. If no argument is given, the n
umber
returned is in the range from 0 to 1; where only 0 is a possible value;
1 will
never be returned. If an argument is supplied, the number returned will
be in
the range from 0 up to this argument, whereas this argument itself is no
t a
possible return value. Regardless of the range, ran is guaranteed to hav
e
exactly 2**30 different return values.
If you call ran multiple times during your program, the sequence of rand
om
numbers will be different each time you invoke your program; however, if
, e.g.
for testing you prefer to always have the same sequence of random number
s you
may issue poke "random_seed",123.
Example
clear screen
c=peek("screenwidth")-1
l=peek("screenheight")
dim col$(8)
for a=0 to 7:read col$(a):next a
data "black","white","red","blue","green","yellow","cyan","magenta"
do
x=ran(c)
y=l-ran(l*exp(-32*((x/c-1/2)**2)))
i=i+1
print color(col$(mod(i,8))) at(x,y) "*";
loop
This example will print a colored bell-curve.
See also
int
------------------------------------------------------------------------
-------
Name
read ? read data from data-statements
Synopsis
read a$,a
?
data "Hello !",7
Description
The read-statement retrieves literal data, which is stored within
data-statements elsewhere in your program.
Example
read num
dim col$(num)
for a=1 to num:read col$(a):next a
clear screen
print "These are the colours known to yabasic:\n"
for a=1 to num
print colour(col$(a)) col$(a)
next a
data 8,"black","white","red","blue"
data "green","yellow","cyan","magenta"
This program prints the names of the colors known to yabasic in those ve
ry
colors.
See also
data, restore
------------------------------------------------------------------------
-------
Name
rectangle ? draw a rectangle
Synopsis
open window 100,100
rectangle 10,10 to 90,90
rectangle 20,20,80,80
rect 20,20,80,80
box 30,30,70,70
clear rectangle 30,30,70,70
fill rectangle 40,40,60,60
clear fill rectangle 60,60,40,40
Description
The rectangle-command (also known as box or rect, for short) draws a rec
tangle;
it accepts four parameters: The x- and y-coordinates of two facing corne
rs of
the rectangle. With the optional clauses clear and fill (which may appea
r
together and in any sequence) the rectangle can be cleared and filled
respectively.
Example
open window 200,200
c=1
do
for phi=0 to pi step 0.1
if (c) then
rectangle 100+100*sin(phi),100+100*cos(phi) to 100-100*sin(phi),10
0-100*cos(phi)
else
clear rectangle 100+100*sin(phi),100+100*cos(phi) to 100-100*sin(p
hi),100-100*cos(phi)
endif
sleep 0.1
next phi
c=not c
loop
This example draws a nice animated pattern; watch it for a couple of hou
rs, to
see how it develops.
See also
open window, open printer, line, circle, triangle
------------------------------------------------------------------------
-------
Name
redim ? create an array prior to its first use. A synonym for dim
Synopsis
See the dim-command.
Description
The redim-command does exactly the same as the dim-command; it is just a
synonym. redim has been around in older versions of basic (not even yaba
sic)
for many years; therefore it is supported in yabasic for compatibility r
easons.
Please refer to the entry for the dim-command for further information.
------------------------------------------------------------------------
-------
Name
rem ? start a comment
Synopsis
rem Hey, this is a comment
# the hash-sign too (at beginning of line)
// even the double slash
' and the single quote (at beginning of line)
print "Not a comment" # This is an error !!
print "Not a comment":// But this is again a valid comment
print "Not a comment" // even this.
print "Not a comment" rem and this !
Description
rem introduces a comment (like # or //), that extends up to the end of t
he
line.
Those comments do not even need a colon (':') in front of them; they (re
m, #, '
(single quite) and //) all behave alike except for # and ', which may on
ly
appear at the very beginning of a line; therefore the fourth example in
the
synopsis above (print "Not a comment" # This is an error !!) is indeed a
n
error.
Note, that rem is an abbreviation for remark. remark however is not a va
lid
command in yabasic.
Finally note, that a comment introduced with '#' may have a special mean
ing
under unix; see the entry for # for details.
Example
#
rem comments on data structures
# are more useful than
// comments on algorithms.
rem
This program does nothing, but in a splendid and well commented way.
See also
#, //
------------------------------------------------------------------------
-------
Name
repeat ? start a repeat-loop
Synopsis
repeat
?
until (?)
Description
The repeat-loop executes all the statements up to the final until-keywor
d over
and over. The loop is executed as long as the condition, which is specif
ied
with the until-clause, becomes true. By construction, the statements wit
hin the
loop are executed at least once.
Example
x=0
clear screen
print "This program will print the numbers from 1 to 10"
repeat
x=x+1
print x
print "Press any key for the next number, or 'q' to quit"
if (inkey$="q") break
until(x=10)
This program is pretty much useless, but self-explanatory.
See also
until, break, while, do
------------------------------------------------------------------------
-------
Name
restore ? reposition the data-pointer
Synopsis
read a,b,c,d,e,f
restore
read g,h,i
restore foo
data 1,2,3
label foo
data 4,5,6
Description
The restore-command may be used to reset the reading of data-statements,
so
that the next read-statement will read data from the first data-statemen
t.
You may specify a label with the restore-command; in that case, the next
read-statement will read data starting at the given label. If the label
is
omitted, reading data will begin with the first data-statement within yo
ur
program.
Example
input "Which language (german/english) ? " l$
if (instr("german",l$)>0) then
restore german
else
restore english
endif
for a=1 to 3
read x,x$
print x,"=",x$
next a
label english
data 1,"one",2,"two",3,"three"
label german
data 1,"eins",2,"zwei",3,"drei"
This program asks to select one of those languages known to me (i.e. eng
lish or
german) and then prints the numbers 1,2 and 3 and their textual equivale
nts in
the chosen language.
See also
read, data, label
------------------------------------------------------------------------
-------
Name
return ? return from a subroutine or a gosub
Synopsis
gosub foo
?
label foo
?
return
sub bar(baz)
?
return quertz
end sub
Description
The return-statement serves two different (albeit somewhat related) purp
oses.
The probably more important use of return is to return control from with
in a
subroutine to the place in your program, where the subroutine has been c
alled.
If the subroutine is declared to return a value, the return-statement mi
ght be
accompanied by a string or number, which constitutes the return value of
the
subroutine.
However, even if the subroutine should return a value, the return-statem
ent
need not carry a value; in that case the subroutine will return 0 or the
empty
string (depending on the type of the subroutine). Moreover, feel free to
place
multiple return-statements within your subroutine; it's a nice way of
controlling the flow of execution.
The second (but historically first) use of return is to return to the po
sition,
where a prior gosub has left off. In that case return may not carry a va
lue.
Example
do
read a$
if (a$="") then
print
end
endif
print mark$(a$)," ";
loop
data "The","quick","brown","fox","jumped"
data "over","the","lazy","dog",""
sub mark$(a$)
if (instr(lower$(a$),"q")) return upper$(a$)
return a$
end sub
This example features a subroutine mark$, that returns its argument in u
pper
case, if it contains the letter "q", or unchanged otherwise. In the test
-text
the word quick will end up being marked as QUICK.
The example above demonstrates return within subroutines; please see gos
ub for
an example of how to use return in this context.
See also
sub, gosub
------------------------------------------------------------------------
-------
Name
reverse ? print reverse (background and foreground colors exchanged)
Synopsis
clear screen
?
print reverse "foo"
Description
reverse may be used to print text in reverse. reverse is not a separate
command, but part of the print-command; it may be included just after th
e print
and can only be issued once that clear screen has been issued.
Example
clear screen
print "1 ";
c=3
do
prim=true
for a=2 to sqrt(c)
if (frac(c/a)=0) then
prim=false
break
endif
next a
if (prim) then
print
print reverse c;
else
print c;
endif
print " ";
c=c+1
loop
This program prints numbers from 1 on and marks each prime number in rev
erse.
See also
at, print color, print, clear screen
------------------------------------------------------------------------
-------
Name
right$() ? return (or change) the right end of a string
Synopsis
print right$(a$,2)
right$(b$,2)="baz"
Description
The right$-function requires two arguments (a string and a number) and r
eturns
the part from the right end of the string, whose length is specified by
its
second argument. So, right$ simply returns the requested number of chars
from
the right end of the given string.
Note, that the right$-function can be assigned to, i.e. it may appear on
the
left hand side of an assignment. In this way it is possible to change a
part of
the variable used within the right$-function. Note, that that way the le
ngth of
the string cannot be changed, i.e. characters might be overwritten, but
not
added. For an example see below.
Example
print "Please enter a length either in inch or centimeter"
print "please add 'in' or 'cm' to mark the unit."
input "Length: " a$
if (right$(a$,2)="in") then
length=val(a$)*2.56
elsif (right$(a$,2)="cm") then
length=val(a$)
else
error "Invalid input: "+a$
endif
This program allows the user to enter a length qualified with a unit (ei
ther
inch or centimeter).
This second example demonstrates the capability to assign to the
right$-function.
a$="Heiho World !"
print a$
right$(a$,7)="dwarfs."
print a$
See also
right$ and mid$
------------------------------------------------------------------------
-------
Name
rinstr() ? find the rightmost occurrence of one string within the other
Synopsis
pos=rinstr("Thequickbrownfox","equi")
pos=rinstr(a$,b$,x)
Description
The rinstr-function accepts two string-arguments and tries to find the s
econd
within the first. However, unlike the instr, the rinstr-function finds t
he
rightmost (or last) occurrence of the string; whereas the instr-function
finds
the leftmost (or first) occurrence. In any case however, the position is
counted from the left.
If you supply a third, numeric argument to the rinstr-function, it will
be used
as a starting point for the search. Therefore rinstr("abcdeabcdeabcde","
e",8)
will return 5, because the search for an "e" starts at position 8 and fi
nds the
first one at position 5.
Example
print rinstr("foofoofoobar","foo")
This simple example will print 7, because it finds the rightmost among t
he
three occurrences of foo within the string. Note, that
print instr("foofoofoobar","foo")
would have printed 1.
See also
instr
------------------------------------------------------------------------
-------
Name
rtrim$() ? trim spaces at the right end of a string
Synopsis
a$=rtrim$(b$)
Description
The rtrim$-function removes all whitespace from the right end of a strin
g and
returns the result.
Example
open 1,"foo"
dim lines$(100)
l=1
while(not eof(1))
input #1 a$
a$=rtrim$(a$)
if (right$(line$,1)="\\") then
line$=line$+" "+a$
else
lines$(l)=line$
l=l+1
line$=a$
endif
end while
print "Read ",l," lines"
This example reads the file foo allowing for continuation lines, which a
re
marked by a \, which appears as the last character on a line. For conven
ience
whitespace at the right end of a line is trimmed with rtrim.
See also
ltrim$, trim$
S
screen ? as clear screen clears the text window
seek() ? change the position within an open file
sig() ? return the sign of its argument
sin() ? return the sine of its single argument
sleep ? pause, sleep, wait for the specified number of seconds
split() ? split a string into many strings
sqr() ? compute the square of its argument
sqrt() ? compute the square root of its argument
static ? preserves the value of a variable between calls to a subroutine
step ? specifies the increment step in a for-loop
str$() ? convert a number into a string
sub ? declare a user defined subroutine
switch ? select one of many alternatives depending on a value
system() ? hand a statement over to your operating system and return its
exitcode
system$() ? hand a statement over to your operating system and return it
s
output
Name
screen ? as clear screen clears the text window
Synopsis
clear screen
Description
The keyword screen appears only within the sequence clear screen; please
see
there for a description.
See also
clear screen
------------------------------------------------------------------------
-------
Name
seek() ? change the position within an open file
Synopsis
open 1,"foo"
seek #1,q
seek #1,x,"begin"
seek #1,y,"end"
seek #1,z,"here"
Description
The seek-command changes the position, where the next input (or peek) st
atement
will read from an open file. Usually files are read from the beginning t
o the
end sequentially; however sometimes you may want to depart from this sim
ple
scheme. This can be done with the seek-command, allowing you to change t
he
position, where the next piece of data will be read from the file.
seek accepts two or three arguments: The first one is the number of an a
lready
open file. The second one is the position where the next read from the f
ile
will start. The third argument is optional and specifies the the point f
rom
where the position (the second argument) will count. It can be one of:
begin
Count from the beginning of the file.
end
Count from the end of the file.
here
Count from the current position within the file.
Example
open #1,"count.dat","w"
for a=1 to 10
print #1,"00000000";
if (a<10) print #1,";";
next a
dim count(10)
do
x=int(ran(10))
i=i+1
if (mod(i,1000)=0) print ".";
count(x)=count(x)+1
curr$=right$("00000000"+str$(count(x)),8)
seek #1,9*x,"begin"
print #1,curr$;
loop
This example increments randomly one of ten counters (in the array count
());
however, the result is always kept and updated within the file count.dat
, so
even in case of an unexpected interrupt, the result will not be lost.
See also
tell, open, print, peek
------------------------------------------------------------------------
-------
Name
sig() ? return the sign of its argument
Synopsis
a=sig(b)
Description
Return +1, -1 or 0, if the single argument is positive, negative or zero
.
Example
clear screen
dim c$(3):c$(1)="red":c$(2)="white":c$(3)="green"
do
num=ran(100)-50
print color(c$(2+sig(num))) num
loop
This program prints an infinite sequence of random number; positive numb
ers are
printed in green, negative numbers are printed red (an exact zero would
be
printed white). (With a little extra work, this program could be easily
extended into a brokerage system)
See also
abs, int, frac
------------------------------------------------------------------------
-------
Name
sin() ? return the sine of its single argument
Synopsis
y=sin(angle)
Description
The sin-function expects an angle (in radians, not degrees) and returns
its
sine.
Example
open window 200,200
new curve
for phi=0 to 2*pi step 0.1
line to 100+90*sin(phi),100+90*cos(phi)
next phi
close curve
This program draws a circle (ignoring the existence of the circle-comman
d).
See also
asin, cos
------------------------------------------------------------------------
-------
Name
sleep ? pause, sleep, wait for the specified number of seconds
Synopsis
sleep 4
Description
The sleep-command has many different names: You may write pause, sleep o
r wait
interchangeably; whatever you write, yabasic will always do exactly the
same.
Therefore you should refer to the entry for the pause-function for furth
er
information.
------------------------------------------------------------------------
-------
Name
split() ? split a string into many strings
Synopsis
dim w$(10)
?
num=split(a$,w$())
num=split(a$,w$(),s$)
Description
The split-function requires a string (containing the text to be split),
a
reference to a string-array (which will receive the resulting strings, i
.e. the
tokens) and an optional string (with a set of characters, at which to sp
lit,
i.e. the delimiters).
The split-function regards its first argument (a string) as a list of to
kens
separated by delimiters and it will store the list of tokens within the
array-reference you have supplied. Note, that the array, which is passed
as a
reference (w$() in the synopsis), will be resized accordingly, so that y
ou
don't have to figure out the number of tokens in advance. The element at
position zero (i.e. w$(0)) will not be used.
normally (i.e. if you omit the third, which is the delimiter-argument) t
he
function will regard space or tab as delimiters for tokens; however by
supplying a third argument, you may split at any single of the character
s
within this string. E.g. if you supply ":;" as the third argument, then
colon
(:) or semicolon (;) will delimit tokens.
Note, that a sequence of separator-characters will produce a sequence of
empty
tokens; that way, the number of tokens returned will always be one plus
the
number of separator characters contained within the string. Refer to the
closely related token-function, if you do not like this behaviour. In so
me way,
the split-function focuses on the separators (other than the token-funct
ion,
which focuses on the tokens), hence its name.
The second argument is a reference on a string-array, where the tokens w
ill be
stored; this array will be expanded (or shrunk) to have room for all tok
ens, if
necessary.
The first argument finally contains the text, that will be split into to
kens.
The split-function returns the number of tokens that have been found.
Please see the examples below for some hints on the exact behaviour of t
he
split-function and how it differs from the token-function:
Example
print "This program will help you to understand, how the"
print "split()-function exactly works and how it behaves"
print "in certain special cases."
print
print "Please enter a line containing tokens separated"
print "by either '=' or '-'"
dim t$(10)
do
print
input "Please enter a line: " l$
num=split(l$,t$(),"=-")
print num," Tokens: ";
for a=1 to num
if (t$(a)="") then
print "(EMPTY)";
else
print t$(a);
endif
if (a<num) print ",";
next a
print
loop
This program prints the following output:
Please enter a line: a
1 Tokens: a
Please enter a line:
0 Tokens:
Please enter a line: ab
1 Tokens: ab
Please enter a line: a=b
2 Tokens: a,b
Please enter a line: a-
2 Tokens: a,(EMPTY)
Please enter a line: a-=
3 Tokens: a,(EMPTY),(EMPTY)
Please enter a line: =a-
3 Tokens: (EMPTY),a,(EMPTY)
Please enter a line: a=-b
3 Tokens: a,(EMPTY),b
Please enter a line: a--b-
4 Tokens: a,(EMPTY),b,(EMPTY)
Please enter a line: -a==b-c==
7 Tokens: (EMPTY),a,(EMPTY),b,c,(EMPTY),(EMPTY)
See also
token
------------------------------------------------------------------------
-------
Name
sqr() ? compute the square of its argument
Synopsis
a=sqr(b)
Description
The sqr-function computes the square of its numerical argument (i.e. it
multiplies its argument with itself).
Example
for a=1 to 10
print a,sqr(a),a**2
next a
As you may see from the output, sqr can be written as **2 (or ^2) too.
See also
sqrt, **, ^
------------------------------------------------------------------------
-------
Name
sqrt() ? compute the square root of its argument
Synopsis
to be written
Description
The sqrt-function computes the square root of its numerical argument.
Example
for a=1 to 5
print a,sqrt(a),a**(1/2)
next a
As you may see from the output, sqrt can be written as **(1/2) (or ^(1/2
)) too.
See also
sqr, **, ^
------------------------------------------------------------------------
-------
Name
static ? preserves the value of a variable between calls to a subroutine
Synopsis
sub foo()
static a
?
end sub
Description
The static keyword can be used within subroutines to mark variables as s
tatic.
This has two effects: First, the variable is local to the subroutine, i.
e. its
value is not know outside the subroutine (this is the effect of the loca
l
keyword). Second, the static-keyword arranges things, so that the variab
le
keeps its value between invocations of the subroutine (this is different
from
the local-keyword).
Example
foo()
foo()
foo()
sub foo()
static a
local b
a=a+1
b=b+1
print a,b
end sub
This program shows the difference between static and local variables wit
hin a
subroutine; it produces this output:
1 1
2 1
3 1
The output shows, that the static variable a keeps its value between sub
routine
calls, whereas b is initialized with the value 0 at every call to the
subroutine foo.
See also
sub, local
------------------------------------------------------------------------
-------
Name
step ? specifies the increment step in a for-loop
Synopsis
for a=1 to 10 step 3
?
next a
Description
Specify, by which amount the loop-variable of a for-loop will be increme
nted at
each step.
The step (as well as the lower and upper bound) are computed anew in eac
h step;
this is not common, but possible, as the example below demonstrates.
Example
for x=1 to 1000 step y
y=x+y
print x," ",y," ";
next x
print
This program computes the fibonacci numbers between 1 and 1000.
See also
for
------------------------------------------------------------------------
-------
Name
str$() ? convert a number into a string
Synopsis
a$=str$(a)
b$=str$(x,"##.###")
b$=str$(x,"###,###.##")
b$=str$(x,"###,###.##","_.")
Description
The str$-function accepts a numeric argument and returns it as a string.
This
conversion between number and string can be controlled with the optional
third
argument (the format argument). See the following table of examples to l
earn
about valid values of this argument. Note, that those examples fall in o
ne of
two categories: C-style and basic-style; the first 4 examples in the tab
le
below are C-style, the rest of the examples are basic-style. For more
information on the C-style formats, you may refer to your favorite
documentation on the C programming language. The basic-style formats are
much
simpler, they just depict the desired output, marking digits with '#'; g
roups
of (usually three) digits may be separated with colons (','), the decima
l dot
must be marked by a literal dot ('.'). Moreover these characters (colons
and
dot) may be replaced by other characters to satisfy the needs of non-eng
lish
(e.g. german) languages; see the examples below.
Note, that for clarity, each space in the result has been replaced by th
e
letter 'x', because it would be hard to figure out, how many spaces are
produced exactly otherwise.
Table 7.2. Examples for the format argument
+-----------------------------------------------------------------------
------+
| Example | Result for |
|
| string | converting | Description
|
| | 1000*pi |
|
|-------------+------------+--------------------------------------------
------|
| | |The '2' determines the minimum length of the
|
|%2.5f |3141.59265 |output; but if needed (as in the example) th
e |
| | |output can be longer. The '5' is the number
of |
| | |digits after the decimal point.
|
|-------------+------------+--------------------------------------------
------|
| | |Two spaces (which appear as 'x') are added t
o pad |
|%12.5f |xx3141.59265|the output to the requested length of 12
|
| | |characters.
|
|-------------+------------+--------------------------------------------
------|
| | |The 'g' requests, that the precision ('5')
|
|%012.5g |0000003141.6|specifies the overall number of digits (befo
re and|
| | |after the decimal point).
|
|-------------+------------+--------------------------------------------
------|
| | |The '-' requests the output to be left-cente
red |
|%-12.5f |3141.59265xx|(therefore the filling space appears at the
|
| | |right).
|
|-------------+------------+--------------------------------------------
------|
| | |Each '#' specifies a digit (either before or
after|
| | |the dot), the '.' specifies the position of
the |
|#####.## |x3141.59 |dot. As 1000*pi does not have enough digits,
the 5|
| | |requested digits before the dot are filled u
p with|
| | |a space (which shows up as an 'x').
|
|-------------+------------+--------------------------------------------
------|
|##,###.## |x3,141.59 |Nearly the same as above, but the colon from
the |
| | |format shows up within the result.
|
|-------------+------------+--------------------------------------------
------|
|##,###.## and| |
|
|an additional|x3.141,59 |Similar to the example above, but colon and
dot |
|argument of | |are replaced with dot and colon respectively
. |
|".," | |
|
|-------------+------------+--------------------------------------------
------|
|##,###.## and| |Similar to the example above, but colon and
dot |
|an additional|x3_141,59 |are replaced with underscore and colon
|
|argument of | |respectively.
|
|"_," | |
|
|-------------+------------+--------------------------------------------
------|
| | |The format string does not contain a dot, an
d |
|##### |x3142 |therefore the result does not have any fract
ional |
| | |digits.
|
|-------------+------------+--------------------------------------------
------|
| | |As 1000*pi has 4 digits in front of the deci
mal |
|##.### |##.### |dot and the format only specifies 2, yabasic
does |
| | |not know what to do; therefore it chooses ju
st to |
| | |reproduce the format string.
|
+-----------------------------------------------------------------------
------+
Example
do
input "Please enter a format string: " f$
a$=str$(1000*pi,f$)
for a=1 to len(a$)
if (mid$(a$,a,1)=" ") mid$(a$,a,1)="x"
next a
print a$
loop
This is the program, that has been used to get the results shown in the
table
above.
See also
print, using
------------------------------------------------------------------------
-------
Name
sub ? declare a user defined subroutine
Synopsis
foo(2,"hello")
?
sub foo(bar,baz$)
?
return qux
?
end sub
Description
The sub-keyword starts the definition of a user defined subroutine. With
user
defined subroutines you are able to somewhat extend yabasic with your ow
n
commands or functions. A subroutine accepts arguments (numbers or string
s) and
returns a number or a string (however, you are not required to assign th
e value
returned to a variable).
The name of the subroutine follows after the keyword sub. If the name (i
n the
synopsis: foo) ends on a '$', the subroutine should return a string (wit
h the
return-statement), otherwise a number.
After the name of the subroutine yabasic requires a pair of braces; with
in
those braces you may specify a list of parameters, for which values can
(but
need not) be included when calling the subroutine. If you omit one of th
ose
parameters when calling such a subroutine, it assumes the value zero (fo
r
numeric parameters) or the empty string (for string-parameters). However
from
the special variable numparams you may find out, how many arguments have
really
been passed when calling the subroutine.
Parameters of a subroutine are always local variables (see the keyword l
ocal
for more explanation).
From within the subroutine you may return any time with the keyword retu
rn;
along with the return-keyword you may specify the return value. Note tha
t more
than one return is allowed within a single subroutine.
Finally, the keyword end sub ends the subroutine definition. Note, that
the
definition of a subroutine need not appear within the program before the
first
call to this sub.
Note
As braces have two uses in yabasic (i.e. for supplying arguments to a
subroutine as well as to list the indices of an array). yabasic can not
tell
apart an array from a subroutine with the same name. Therefore you canno
t
define a subroutine with the same name as an array !
Example
p=2
do
if (is_prime(p)) print p
p=p+1
loop
sub is_prime(a)
local b
for b=2 to sqrt(a)
if (frac(a/b)=0) return false
next b
return true
end sub
This example is not the recommended way to compute prime numbers. Howeve
r it
gives a nice demonstration of using a subroutine.
See also
local, static, peek
------------------------------------------------------------------------
-------
Name
switch ? select one of many alternatives depending on a value
Synopsis
switch a
case 1
case 2
?
end switch
?
switch a$
case "a"
case "b"
end switch
Description
The switch-statement selects one of many codepaths depending on a numeri
cal or
string expression. I.e. it takes an expression (either numeric or string
) and
compares it with a series of values, each wrapped within a case-clause.
If the
expression equals the value given in a case-clause, the subsequent state
ments
are executed.
The default-clause allows one to specify commands, which should be execu
ted, if
none of case-clauses matches.
Note, that many case-clauses might be clustered (e.g. case "a":case "b":
case
"c"). Or put another way: You need a break-statement at the end of a
case-branch, if you do not want to run into the next case.
Example
input "Please enter a single digit: " n
switch n
case 0:print "zero":break
case 1:print "one":break
case 2:print "two":break
case 3:print "three":break
case 4:print "four":break
case 5:case 6: case 7:case 8:case 9
print "Much !":break
default:print "Hey ! That was more than a single digit !"
end switch
This example translates a single digit into a string; note, how the case
s 5 to
7 are clustered.
See also
switch, case, break
------------------------------------------------------------------------
-------
Name
system() ? hand a statement over to your operating system and return its
exitcode
Synopsis
ret=system("foo")
system("bar")
Description
The system-command accepts a single string argument, which specifies a c
ommand
to be executed. The function will return the exitcode of the command; it
s
output (if any) will be lost.
Example
print "Please enter the name of the file, that should be deleted."
input f$
if (system("rm "+f$+" >/dev/null 2>&1")) then
print "Error !"
else
print "okay."
endif
This program is Unix-specific: It uses the Unix-command rm to remove a f
ile.
See also
system$
------------------------------------------------------------------------
-------
Name
system$() ? hand a statement over to your operating system and return it
s
output
Synopsis
print system$("dir")
Description
The system$-command accepts a single string argument, specifying a comma
nd,
that can be found and executed by your operating system. It returns the
output
of this command as one big string.
Example
input "Please enter the name of a directory: " d$
print
print "This is the contents of the '"+d$+"':"
print system$("dir "+d$)
This example lists the contents of a directory, employing the dir-comman
d
(which is about the only program, that is known under Unix as well as Wi
ndows).
See also
system, chomp
T
tan() ? return the tangent of its argument
tell ? get the current position within an open file
text ? write text into your graphic-window
then ? tell the long from the short form of the if-statement
time$ ? return a string containing the current time
to ? this keyword appears as part of other statements
token() ? split a string into multiple strings
triangle ? draw a triangle
trim$() ? remove leading and trailing spaces from its argument
true ? a constant with the value of 1
Name
tan() ? return the tangent of its argument
Synopsis
foo=tan(bar)
Description
The tan-function computes the tangent of its arguments (which should be
specified in radians).
Example
for a=0 to 45
print tan(a*pi/180)
next a
This example simply prints the tangent of all angles between 0 and 45 de
grees.
See also
atan, sin
------------------------------------------------------------------------
-------
Name
tell ? get the current position within an open file
Synopsis
open #1,"foo"
?
position=tell(#1)
Description
The tell-function requires the number of an open file as an argument. It
returns the position (counted in bytes, starting from the beginning of t
he
file) where the next read will start.
Example
open #1,"foo","w"
print #1 "Hello World !"
close #1
open #1,"foo"
seek #1,0,"end"
print tell(#1)
close 1
This example (mis)uses tell to get the size of the file. The seek positi
ons the
file pointer at the end of the file, therefore the call to tell returns
the
total length of the file.
See also
tell, open
------------------------------------------------------------------------
-------
Name
text ? write text into your graphic-window
Synopsis
text x,y,"foo"
text x,y,"foo","lb"
text x,y,"foo","cc","font"
text x,y,"foo","font","rt"
Description
The text-commands displays a text-string (the third argument) at the giv
en
position (the first two arguments) within an already opened window. The
font to
be used can be optionally specified as either the fourth or fifth argume
nt
("font" in the example above). A font specified this way will also be us
ed for
any subsequent text-commands, as long as they do not specify a font them
selves.
The fourth or fifth optional argument ("lb" in the example above) can be
used
to specify the alignment of the text with respect to the specified posit
ion.
This argument is always two characters long: The first character specifi
es the
horizontal alignment and can be either l, r or c, which stand for left,
right
or center. The second character specifies the vertical alignment and can
be one
of t, b or c, which stand for top, bottom or center respectively. If you
omit
this alignment argument, the default "lb" applies; however this default
may be
changed with poke "textalign","xx"
Example
open window 500,200
clear screen
data "lt","lc","lb","ct","cc","cb","rt","rc","rb"
for a=1 to 9
read align$
print "Alignment: ",align$
line 50*a-15,100,50*a+15,100
line 50*a,85,50*a,115
text 50*a,100,"Test",align$
inkey$
next a
This program draws nine crosses and writes the same text at each; howeve
r it
goes through all possible nine alignment strings, showing their effect.
See also
open window, peek, poke
------------------------------------------------------------------------
-------
Name
then ? tell the long from the short form of the if-statement
Synopsis
if (a<b) then
?
endif
Description
The keyword then is part of the if-statement; please see there for furth
er
explanations. However, not every if-statement requires the keyword then:
If the
keyword then is present, the if-clause may extend over more than one lin
e, and
the keyword endif is required to end it. If the keyword then is not pres
ent,
the if-statement extends up to the end of the line, and any endif would
be an
error.
Example
if (1<2) then
print "Hello ";
endif
if (2<3) print "world"
if (2<1)
print "!"
This example prints Hello world. Note, that no exclamation mark (!) is p
rinted,
which might come as a surprise and may be changed in future versions of
yabasic
.
See also
if
------------------------------------------------------------------------
-------
Name
time$ ? return a string containing the current time
Synopsis
print time$
print time$()
Description
The time$ function returns the current time in four fields separated by
hyphens
'-'. The fields are:
* The current hour in the range from 0 to 23, padded with zeroes (e.g.
00 or
04) to a length of two characters.
* The number of minutes, padded with zeroes.
* The number of seconds, padded with zeroes.
* The number of seconds, that have elapsed since the program has been
started. This value increases as long as your program runs and is th
erefore
unbound and not padded with zeroes.
At the time of writing this documentation, time$ returns 22-58-53-0. Not
e, that
the first three of the four fields returned by time$ have a fixed width;
therefore it is easy to extract some fields with the usual string-functi
ons
mid$ (and others).
Example
print "Hello it is ",time$
print "An empty for-loop with ten million iterations takes ";
for a=1 to 10000000:next a
print "Now it is ",time$
print peek("secondsrunning")," seconds have passed."
This program benchmarks the for-loop; however, it does not use the fourt
h field
of the string returned by time$, because that string wraps around every
60
seconds; rather the peek "secondsrunning" is queried.
See also
date
------------------------------------------------------------------------
-------
Name
to ? this keyword appears as part of other statements
Synopsis
for a=1 to 100 step 2
?
next a
line x,y to a,b
Description
The to-keyword serves two purposes (which are not related at all):
* within for-statements, to specify the upper bound of the loop.
* Within any graphical command (e.g. line), that requires two points (
i.e.
four numbers) as arguments, a comma ',' might be replaced with the k
eyword
to. I.e. instead of 100,100,200,200 you may write 100,100 to 200,200
in
such commands.
Example
Please see the command listed under "See also" for examples.
See also
for, line, rectangle
------------------------------------------------------------------------
-------
Name
token() ? split a string into multiple strings
Synopsis
dim w$(10)
?
num=token(a$,w$())
num=token(a$,w$(),s$)
Description
The token-function accepts a string (containing the text to be split), a
reference to a string-array (which will receive the resulting strings, i
.e. the
tokens) and an optional string (with a set of characters, at which to sp
lit,
i.e. the delimiters).
The token-function regards its first argument as a list of tokens separa
ted by
delimiters and it will store the list of tokens within the array-referen
ce that
has been supplied. Note, that the array, which is passed as a reference
(w$()
in the synopsis), will be resized accordingly, so that you don't have to
figure
out the number of tokens in advance. The element at position zero (i.e.
w$(0))
will not be used.
Normally (i.e. if you omit the third, the delimiter-argument) the functi
on will
regard space or tab as delimiters for tokens; however by supplying a thi
rd
argument, you may split at any single of the characters within this stri
ng.
E.g. if you supply ":;" as the third argument, then colon (:) or semicol
on (;)
will delimit tokens.
Note, that token will never produce empty tokens, even if two or more
separators follow in sequence. Refer to the closely related split-functi
on, if
you do not like this behaviour. In some way, the token-function focuses
on the
tokens and not on the separators (other than the split-function, which f
ocuses
on the separators).
The second argument is a reference on a string-array, where the tokens w
ill be
stored; this array will be expanded (or shrunk) as necessary to have roo
m for
all tokens.
The first argument finally contains the text, that will be split into to
kens.
The token-function returns the number of tokens, that have been found.
Please see the examples below for some hints on the exact behaviour of t
he
token-function and how it differs from the split-function:
Example
print "This program will help you to understand, how the"
print "token()-function exactly works and how it behaves"
print "in certain special cases."
print
print "Please enter a line containing tokens separated"
print "by either '=' or '-'"
dim t$(10)
do
print
input "Please enter a line: " l$
num=token(l$,t$(),"=-")
print num," Tokens: ";
for a=1 to num
if (t$(a)="") then
print "(EMPTY)";
else
print t$(a);
endif
if (a<num) print ",";
next a
print
loop
This program prints the following output:
Please enter a line: a
1 Tokens: a
Please enter a line:
0 Tokens:
Please enter a line: ab
1 Tokens: ab
Please enter a line: a=b
2 Tokens: a,b
Please enter a line: a-
1 Tokens: a
Please enter a line: a-=
1 Tokens: a
Please enter a line: =a-
1 Tokens: a
Please enter a line: a=-b
2 Tokens: a,b
Please enter a line: a--b-
2 Tokens: a,b
Please enter a line: -a==b-c==
3 Tokens: a,b,c
See also
split
------------------------------------------------------------------------
-------
Name
triangle ? draw a triangle
Synopsis
open window 100,100
triangle 100,100,50,50,100,50
fill triangle 50,100,100,50,200,200
clear fill triangle 20,20,10,10,200,200
Description
The triangle-command draws a triangle; it requires 6 parameters: The x-
and
y-coordinates of the three points making up the triangle. With the optio
nal
keywords clear and fill (which may appear both and in any sequence) the
triangle can be cleared and filled respectively.
Example
open window 200,200
do
phi=phi+0.2
i=i+2
color mod(i,255),mod(85+2*i,255),mod(170+3*i,255)
dx=100*sin(phi):dy=20*cos(phi)
fill triangle 100+20*sin(phi),100+20*cos(phi),100-20*sin(phi),100-20*c
os(phi),100-80*cos(phi),100+80*sin(phi)
sleep 0.1
loop
This example draws a colored triangles until you get exhausted.
See also
open window, open printer, line, circle, rectangle
------------------------------------------------------------------------
-------
Name
trim$() ? remove leading and trailing spaces from its argument
Synopsis
a$=trim$(b$)
Description
The trim$-function removes all whitespace from the left and from the rig
ht end
of a string and returns the result. Calling trim$ is equivalent to calli
ng
rtrim$(ltrim$()).
Example
do
input "Continue ? Please answer yes or no: " a$
a$=lower$(trim$(a$))
if (len(a$)>0 and a$=left$("no",len(a$)) exit
loop
This example asks for an answer (yes or no) and removes spaces with trim
$ to
make the comparison with the string "no" more bulletproof.
See also
ltrim$, rtrim$
------------------------------------------------------------------------
-------
Name
true ? a constant with the value of 1
Synopsis
okay=true
Description
The constant true can be assigned to variables which will later appear i
n
conditions (e.g. an if-statement.
true may also be written as TRUE or even TrUe.
Example
input "Please enter a string of all upper letters: " a$
if (is_upper(a$)) print "Okay"
sub is_upper(a$)
if (a$=upper$(a$)) return true
return false
end sub
See also
false
U
until ? end a repeat-loop
upper$() ? convert a string to upper case
using ? Specify the format for printing a number
Name
until ? end a repeat-loop
Synopsis
repeat
?
until (?)
Description
The until-keyword ends a loop, which has been introduced by the repeat-k
eyword.
until requires a condition in braces (or an expression, see here for det
ails)
as an argument; the loop will continue until this condition evaluates to
true.
Example
c=1
s=1
repeat
l=c
s=-(s+sig(s))
c=c+1/s
print c
until(abs(l-c)<0.000001)
This program calculates the sequence 1/1-1/2+1/3-1/4+1/5-1/6+1/7-1/8+ ?
;
please let me know, if you know against which value this converges.
See also
repeat
------------------------------------------------------------------------
-------
Name
upper$() ? convert a string to upper case
Synopsis
u$=upper$(a$)
Description
The upper$-function accepts a single string argument and converts it to
all
upper case.
Example
line input "Please enter a sentence without the letter 'e': " l$
p=instr(upper$(l$),"E")
if (p) then
l$=lower$(l$)
mid$(l$,p,1)="E"
print "Hey, you are wrong, see here!"
print l$
else
print "Thanks."
endif
This program asks for a sentence and marks the first (if any) occurrence
of the
letter 'e' by converting it to upper case (in contrast to the rest of th
e
sentence, which is converted to lower case).
See also
lower$
------------------------------------------------------------------------
-------
Name
using ? Specify the format for printing a number
Synopsis
print a using "##.###"
print a using("##.###",",.")
Description
The using-keyword may appear as part of the print-statement and specifie
s the
format (e.g. the number of digits before and after the decimal dot), whi
ch
should be used to print the number.
The possible values for the format argument ("##.###" in the synopsis ab
ove)
are described within the entry for the str$-function; especially the sec
ond
line in the synopsis (print a using("##.###",",.")) will become clear af
ter
referring to str$. In fact the using clause is closely related to the
str$-function; the former can always be rewritten using the latter; i.e.
print
foo using bar$ is always equivalent to print str$(foo,bar$). Therefore y
ou
should check out str$ to learn more.
Example
for a=1 to 10
print sqrt(ran(10000*a)) using "#########.#####"
next a
This example prints a column of square roots of random number, nicely al
igned
at the decimal dot.
See also
print, str$
V
val() ? converts a string to a number
Name
val() ? converts a string to a number
Synopsis
x=val(x$)
Description
The val-function checks, if the start of its string argument forms a flo
ating
point number and then returns this number. The string therefore has to s
tart
with digits (only whitespace in front is allowed), otherwise the val-fun
ction
returns zero.
Example
input "Please enter a length, either in inches (in) or centimeters (cm)
" l$
if (right$(l$,2)="in") then
l=val(l$)*2.51
else
l=val(l$)
print "You have entered ",l,"cm."
This example queries for a length and checks, if it has been specified i
n
inches or centimeters. The length is then converted to centimeters.
See also
str$
W
wait ? pause, sleep, wait for the specified number of seconds
wend ? end a while-loop
while ? start a while-loop
window origin ? move the origin of a window
Name
wait ? pause, sleep, wait for the specified number of seconds
Synopsis
wait 4
Description
The wait-command has many different names: You may write pause, sleep or
wait
interchangeably; whatever you write, yabasic will always do exactly the
same.
Therefore you should refer to the entry for the pause-function for furth
er
information.
------------------------------------------------------------------------
-------
Name
wend ? end a while-loop
Synopsis
while(a<b)
?
wend
Description
The wend-keyword marks the end of a while-loop. Please see the while-key
word
for more details.
wend can be written as end while or even end-while.
Example
line input "Please enter a sentence: " a$
p=instr(a$,"e")
while(p)
mid$(a$,p,1)="E"
p=instr(a$,"e")
wend
print a$
This example reads a sentence and converts every occurrence of the lette
r e
into uppercase (E).
See also
while (which is just the following entry).
------------------------------------------------------------------------
-------
Name
while ? start a while-loop
Synopsis
while(?)
?
wend
Description
The while-keyword starts a while-loop, i.e. a loop that is executed as l
ong as
the condition (which is specified in braces after the keyword while) eva
luates
to true.
Note, that the body of such a while-loop will not be executed at all, if
the
condition following the while-keyword is not true initially.
If you want to leave the loop prematurely, you may use the break-stateme
nt.
Example
open #1,"foo"
while(!eof(1))
line input #1 a$
print a$
wend
This program reads the file foo and prints it line by line.
See also
until, break, wend, do
------------------------------------------------------------------------
-------
Name
origin ? move the origin of a window
Synopsis
open window 200,200
origin "cc"
Description
The origin-command applies to graphic windows and moves the origin of th
e
coordinate system to one of nine point within the window. The normal pos
ition
of the origin is in the upper left corner of the window; however in some
cases
this is inconvenient and moving the origin may save you from subtracting
a
constant offset from all of your coordinates.
However, you may not move the origin to an arbitrary position; in horizo
ntal
position there are only three positions: left, center and right, which a
re
decoded by the letters l, c and r. In vertical position the allowed posi
tions
are top, center and bottom; encoded by the letters t, c and b. Taking th
e
letters together, you arrive at a string, which might be passed as an ar
gument
to the command; e.g. "cc" or "rt".
Example
100,100
open window 200,200
window origin "cc"
circle 0,0,60
This example draws a circle, centered at the center of the window.
See also
open window
X
xor() ? compute the exclusive or
Name
xor() ? compute the exclusive or
Synopsis
x=xor(a,b)
Description
The xor computes the bitwise exclusive or of its two numeric arguments.
To
understand the result, both arguments should be viewed as binary numbers
(i.e.
a series of 0 and 1); a bit of the result will then be 1, if exactly one
argument has a 1 and the other has a 0 at this position in their binary
representation.
Note, that both arguments are silently converted to integer values and t
hat
negative numbers have their own binary representation and may lead to
unexpected results when passed to and.
Example
print xor(7,4)
This will print 3. This result is obvious, if you note, that the binary
representation of 7 and 4 are 111 and 100 respectively; this will yield
011 in
binary representation or 2 as decimal.
The eor-function is the same as the xor function; both are synonymous; h
owever
they have each their own description, so you may check out the entry of
eor for
a slightly different view.
See also
and, or, eor, not
Special characters
# ? either a comment or a marker for a file-number
// ? starts a comment
@ ? synonymous to at
: ? separate commands from each other
; ? suppress the implicit newline after a print-statement
** or ^ ? raise its first argument to the power of its second
Name
# ? either a comment or a marker for a file-number
Synopsis
# This is a comment, but the line below not !
open #1,"foo"
Description
The hash ('#') has two totally unrelated uses:
* A hash might appear in commands related with file-io. yabasic uses s
imple
numbers to refer to open files (within input, print, peek or eof). I
n those
commands the hash may precede the number, which species the file. Pl
ease
see those commands for further information and examples; the rest of
this
entry is about the second use (as a comment).
* As the very first character within a line, a hash introduces comment
s
(similar to rem).
'#' as a comment is common in most scripting languages and has a special
use
under Unix: If the very first line of any Unix-program begins with the
character sequence '#!' ("she-bang", no spaces allowed), the rest of the
line
is taken as the program that should be used to execute the script. I.e.
if your
yabasic-program starts with '#!/usr/local/bin/yabasic', the program /usr
/local/
bin/yabasic will be invoked to execute the rest of the program. As a rem
ark for
windows-users: This mechanism ensures, that yabasic will be invoked to e
xecute
your program; the ending of the file (e.g. .yab) will be ignored by Unix
.
Example
# This line is a valid comment
print "Hello " : # But this is a syntax error, because
print "World!" : # the hash is not the first character !
Note, that this example will produce a syntax error and is not a valid p
rogram
!
See also
input, print, peek or eof, //, rem
------------------------------------------------------------------------
-------
Name
// ? starts a comment
Synopsis
// This is a comment !
Description
The double-slash ('//') is (besides REM and '#') the third way to start
a
comment. '//' is the latest and greatest in the field of commenting and
allows
yabasic to catch up with such cool languages like C++ and Java.
Example
// Another comment.
print "Hello world !" // Another comment
Unlike the example given for '#' this example is syntactically correct a
nd will
not produce an error.
See also
#, rem
------------------------------------------------------------------------
-------
Name
@ ? synonymous to at
Synopsis
clear screen
?
print @(a,b)
Description
As '@' is simply a synonym for at, please see at for further information
.
See also
at
------------------------------------------------------------------------
-------
Name
: ? separate commands from each other
Synopsis
print "Hello ":print "World"
Description
The colon (':') separates multiple commands on a single line.
The colon and the newline-character have mostly the same effect, only th
at the
latter, well, starts a new line too. The only other difference is their
effect
within the (so-called) short if, which is an if-statement without the ke
yword
then. Please see the entry for if for more details.
Example
if (a<10) print "Hello ":print "World !"
This example demonstrates the difference between colon and newline as de
scribed
above.
See also
if
------------------------------------------------------------------------
-------
Name
; ? suppress the implicit newline after a print-statement
Synopsis
print "foo",bar;
Description
The semicolon (';') may only appear at the last position within a print
-statement. It suppresses the implicit newline, which yabasic normally a
dds
after each print-statement.
Put another way: Normally the output of each print-statement appears on
a line
by itself. If you rather want the output of many print-statements to app
ear on
a single line, you should end the print-statement with a semicolon.
Example
print "Hello ";:print "World !"
This example prints Hello World ! in a single line.
See also
print
------------------------------------------------------------------------
-------
Name
** or ^ ? raise its first argument to the power of its second
Synopsis
print 2**b
print 3^4
Description
** (or ^, which is an exact synonym), is the arithmetic operator of
exponentiation; it requires one number to its left and a second one to i
ts
right; ** then raises the first argument to the power of the second and
returns
the result. The result will only be computed if it yields a real number
(as
opposed to a complex number); this means, that the power can not be comp
uted,
if the first argument is negative and the second one is fractional. On t
he
other hand, the second argument can be fractional, if the first one ist
positive; this means, that ** may be used to compute arbitrary roots: e.
g.
x**0.5 computes the square root of x.
Example
print 2**0.5
See also
sqrt
Reserved Words
Here is a list of all reserved words in yabasic. Please make sure, that
you do
not try to use one of them as the name of a variable or subroutine. Or,
the
other way around: If you get some mysterious error from yabasic and you
just
can't figure out why, then you might be using one of the reserved words
below,
without knowing.
Anyway, here is the list:
ABS ACOS AND ARRAYDIM ARRAYDIMENSION
ARRAYSIZE AS ASC ASIN AT
ATAN BEEP BELL BIN$ BIND
BITBLIT BITBLIT$ BITBLT BITBLT$ BOX
BREAK CASE CHR$ CIRCLE CLEAR
CLOSE COLOR COLOUR COMPILE CONTINUE
COS CURVE DATA DATE$ DEC
DEFAULT DIM DO DOT ELSE
ELSEIF ELSIF END ENDIF EOF
EOR ERROR EXECUTE EXECUTE$ EXIT
EXP EXPORT FI FILL FILLED
FOR FRAC GETBIT$ GETSCREEN$ GLOB
GOSUB GOTO HEX$ IF INKEY$
INPUT INSTR INT INTERRUPT LABEL
LEFT$ LEN LET LINE LOCAL
LOG LOOP LOWER$ LTRIM$ MAX
MID$ MIN MOD MOUSEB MOUSEBUTTON
MOUSEMOD MOUSEMODIFIER MOUSEX MOUSEY NEW
NEXT NOT NUMPARAM ON OPEN
OR ORIGIN PAUSE PEEK PEEK$
POKE PRINT PRINTER PUTBIT PUTSCREEN
RAN READ READING RECT RECTANGLE
REDIM REPEAT RESTORE RETURN REVERSE
RIGHT$ RINSTR RTRIM$ SCREEN SEEK
SIG SIN SLEEP SPLIT SPLIT$
SQR SQRT STATIC STEP STR$
SUB SUBROUTINE SWITCH SYSTEM SYSTEM$
TAN TELL TEXT THEN TIME$
TO TOKEN TOKEN$ TRIANGLE TRIM$
UNTIL UPPER$ USING VAL WAIT
WEND WHILE WINDOW WRITING XOR
Please see here for explanations on how to use these words in yabasic.
Chapter 8. Some general concepts and terms
Logical shortcuts
Conditions and expressions
References on arrays
Specifying Filenames under Windows
Escape-sequences
Creating a standalone program from your yabasic-program
This chapter presents some general concepts and terms, which deserve a
description on their own, but are not associated with a single command o
r
function in yabasic. Most of these topics do not lend themselves to be r
ead
alone, rather they might be read (or skimmed) as background material if
an
entry from the alphabetical list of commands refers to them.
Logical shortcuts
Logical shortcuts are no special language construct and there is no keyw
ord for
them; they are just a way to evaluate logical expressions. Logical expre
ssions
(i.e. a series of conditions or comparisons joined by and or or) are onl
y
evaluated until the final result of the expression can be determined. An
example:
if (a<>0 and b/a>2) print "b is at least twice as big as a"
The logical expression a<>0 and b/a>2 consists of two comparisons, both
of
which must be true, if the print statement should be executed. Now, if t
he
first comparison (a<>0) is false, the whole logical expression can never
be
true and the second comparison (b/a>2) need not be evaluated.
This is exactly, how yabasic behaves: The evaluation of a composed logic
al
expressions is terminated immediately, as soon as the final result can b
e
deduced from the already evaluated parts.
In practice, this has the following consequences:
* If two or more comparisons are joined with and and one comparison re
sults
in false, the logical expression is evaluated no further and the ove
rall
result is false.
* If two or more comparisons are joined with or and one comparison res
ults in
true, the logical expression is evaluated no further and the result
is
true.
?Nice, but whats this good for ??, I hear you say. Well, just have anoth
er look
at the example, especially the second comparison (b/a>2); dividing b by
a is
potentially hazardous: If a equals zero, the expression will cause an er
ror and
your program will terminate. To avoid this, the first part of the compar
ison (a
<>0) checks, if the second one can be evaluated without risk. This pre-c
hecking
is the most common usage and primary motivation for logical shortcuts (a
nd the
reason why most programming languages implement them).
Conditions and expressions
Well, bottomline there is no difference or distinction between condition
s and
expressions, at least as yabasic is concerned. So you may assign the res
ult of
comparisons to variables or use an arithmetic expression or a simple var
iable
within a condition (e.g. within an if-statement). So the constructs show
n in
the example below are all totally valid:
input "Please enter a number between 1 and 10: " a
rem Assigning the result of a comparison to a variable
okay=a>=1 and a<=10
rem Use a variable within an if-statement
if (not okay) error "Wrong, wrong !"
So conditions and expressions are really the same thing (at least as lon
g as
yabasic is concerned). Therefore the terms conditions and expression can
really
be used interchangeably, at least in theory. In reality the term conditi
on is
used in connection with if or while whereas the term expression tends to
be
used more often within arithmetic context.
References on arrays
References on arrays are the only way to refer to an array as a whole an
d to
pass it to subroutines or functions like arraydim or arraysize. Whereas
(for
example) a(2) designates the second element of the array a, a() (with em
pty
braces) refers to the array a itself. a() is called an array reference.
If you pass an array reference to one of your own subroutines, you need
to be
aware, that the subroutine will be able to modify the array you have pas
sed in.
So passing an array reference does not create a copy of the array; this
has
some interesting consequences:
* Speed and space: Creating a copy of an array would be a time (and re
source)
consuming operation; passing just a reference is cheap and fast.
* Returning many values: A subroutine, that wants to give back more th
an one
value, may require an array reference among its arguments and then s
tore
its many return values within this array. This is the only way to re
turn
more than one value from a subroutine.
Specifying Filenames under Windows
As you probably know, windows uses the character '\' to separate the
directories within a pathname; an example would be C:\yabasic\yabasic.ex
e (the
usual location of the yabasic executable). However, the very same charac
ter '\'
is used to construct escape sequences, not only in yabasic but in most o
ther
programming languages.
Therefore the string "C:\t.dat" does not specify the file t.dat within t
he
directory C:; this is because the sequence '\t' is translated into the
tab-character. To specify this filename, you need to use the string "C:\
\t.dat"
(note the double slash '\\').
Escape-sequences
Escape-sequences are the preferred way of specifying 'special' character
s. They
are introduced by the '\'-character and followed by one of a few regular
letters, e.g. '\n' or '\r' (see the table below).
Escape-sequences may occur within any string at any position; they are r
eplaced
at parsetime (opposed to runtime), i.e. as soon as yabasic discovers the
string, with their corresponding special character. As a consequence of
this
len("\a") returns 1, because yabasic replaces "\a" with the matching spe
cial
character just before the program executes.
Table 8.1. Escape sequences
+--------------------------------------------+
|Escape Sequence| Matching special character |
|---------------+----------------------------|
|\n |newline |
|---------------+----------------------------|
|\t |tabulator |
|---------------+----------------------------|
|\v |vertical tabulator |
|---------------+----------------------------|
|\b |backspace |
|---------------+----------------------------|
|\r |carriage return |
|---------------+----------------------------|
|\f |formfeed |
|---------------+----------------------------|
|\a |alert (i.e. a beeping sound)|
|---------------+----------------------------|
|\\ |backslash |
|---------------+----------------------------|
|\' |single quote |
|---------------+----------------------------|
|\" |double quote |
|---------------+----------------------------|
|\xHEX |chr$(HEX) (see below) |
+--------------------------------------------+
Note, that an escape sequences of the form \xHEX allows one to encode ar
bitrary
characters as long as you know their position (as a hex-number) within t
he
ascii-charset: For example \x012 is transformed into the character chr$(
18) (or
chr$(dec("12",16)). Note that \x requires a hexa-decimal number (and the
hexa-decimal string "12" corresponds to the decimal number 18).
Creating a standalone program from your yabasic-program
Creating a standalone-program from the command line
Creating a standalone-program from within your program
Downsides of creating a standalone program
See also
Note
The bind-feature, which is described below, is at an experimental stage
right
now. It works (at least for me !) under Windows and Linux, but I cannot
even
promise it for other variants of Unix. However, if it does not work for
your
Unix, I will at least try to make it work, if you give me sufficient
information of your system.
Sometimes you may want to give one of your yabasic-programs to other peo
ple.
However, what if those other people do not have yabasic installed ? In t
hat
case you may create a standalone-program from your yabasic-program, i.e.
an
executable, that may be executed on its own, standalone, even (and espec
ially
!) on computers, that do not have yabasic installed. Having created a
standalone program, you may pass it around like any other program (e.g.
one
written in C) and you can be sure that your program will execute right a
way.
Such a standalone-program is simply created by copying the full yabasic
-interpreter and your yabasic-program (plus all the libraries it does im
port)
together into a single, new program, whose name might be chosen at will
(under
windows of course it should have the ending .exe). If you decide to crea
te a
standalone-program, there are three bits in yabasic, that you may use:
* The bind-command, which does the actual job of creating the standalo
ne
program from the yabasic-interpreter and your program.
* The command-line Option --bind (see options), which does the same fr
om the
command-line.
* The special peek("isbound"), which may be used to check, if the yaba
sic
-program containing this peek is bound to the interpreter as part of
a
standalone program.
With these bits you know enough to create a standalone-program. Actually
there
are two ways to do this: on the command line and from within your progra
m.
Creating a standalone-program from the command line
Let's say you have the following very simple program within the file foo
.yab:
print "Hello World !"
Normally you would start this yabasic-program by typing yabasic foo.yab
and as
a result the string Hello World ! would appear on your screen. However,
to
create a standalone-program from foo.yab you would type:
yabasic -bind foo.exe foo.yab
This command does not execute your program foo.yab but rather create a
standalone-program foo.exe. Note: under Unix you would probably name the
standalone program foo or such, omitting the windows-specific ending .ex
e.
Yabasic will confirm by printing something like: ---Info: Successfully b
ound
'yabasic' and 'foo.yab' into 'foo.exe'.
After that you will find a program foo.exe (which must be made executabl
e with
the chmod-command under Unix first). Now, executing this program foo.exe
(or
foo under Unix) will produce the output Hello World !.
This newly created program foo.exe might be passed around to anyone, eve
n if he
does not have yabasic installed.
Creating a standalone-program from within your program
It is possible to write a yabasic-program, that binds itself to the yaba
sic
-interpreter. Here is an example:
if (!peek("isbound")) then
bind "foo"
print "Successfully created the standalone executable 'foo' !"
exit
endif
print "Hello World !"
If you run this program (which may be saved in the file foo.yab) via yab
asic
foo.yab, the peek("isbound") in the first line will check, if the progra
m is
already part of a standalone-program. If not (i.e. if the yabasic-interp
reter
and the yabasic-program are separate files) the bind-command will create
a
standalone program foo containing both. As a result you would see the ou
tput
Successfully created the standalone executable 'foo' !. Note: Under Wind
ows you
would probably choose the filename foo.exe.
Now, if you run this standalone executable foo (or foo.exe), the very sa
me
yabasic-program that is shown above will be executed again. However, thi
s time
the peek("isbound") will return TRUE and therefore the condition of the
if-statement is false and the three lines after then are not executed. R
ather
the last print-statement will run, and you will see the output Hello Wor
ld !.
That way a yabasic-program may turn itself into a standalone-program.
Downsides of creating a standalone program
Now, before you go out and turn all your yabasic-programs into standalon
e
programs, please take a second to consider the downsides of doing so:
* The new standalone program will be at least as big as the interprete
r
itself, so you need to pass a few hundred kilobytes around, just to
save
people from having to install yabasic themselves.
* There is no easy way to extract your yabasic-program from within the
standalone program: If you ever want to change it, you need to have
it
around separately.
* If a new version of yabasic becomes available, again you need to rec
reate
all of your standalone programs to take advantage of bugfixes and
improvements.
So, being able to create a standalone program is certainly a good thing,
but
certainly not a silver bullet.
See also
The bind-command, the peek-function and the command line options.
Chapter 9. A few example programs
A very simple program
The demo of yabasic
A very simple program
The program below is a very simple program:
repeat
input "Please enter the first number, to add " a
input "Please enter the second number, to add " b
print a+b
until(a=0 and b=0)
This program requests two numbers, which it than adds. The process is re
peated
until you enter zero (or nothing) twice.
The demo of yabasic
The listing below is the demo of yabasic. Note, that parts of this demo
have
been written before some of the more advanced features (e.g subroutines)
of
yabasic have been implemented. So please do not take this as a particula
r good
example of yabasic-code.
//
// This program demos yabasic
//
// Check, if screen is large enough
clear screen
sw=peek("screenwidth"):sh=peek("screenheight")
if (sw<78 or sh<24) then
print
print " Sorry, but your screen is to small to run this demo !"
print
end
endif
sw=78:sh=24
// Initialize everything
restore mmdata
read mmnum:dim mmtext$(mmnum)
for a=1 to mmnum:read mmtext$(a):next a
// Main loop selection of demo
ysel=1
label mainloop
clear screen
print colour("cyan","magenta") at(7,2) "################################
"
print colour("cyan","magenta") at(7,3) "################################
"
print colour("cyan","magenta") at(7,4) "################################
"
print colour("yellow","blue") at(8,3) " This is the demo for yabasic "
yoff=7
for a=1 to mmnum
if (a=mmnum) then ydisp=1:else ydisp=0:fi
if (a=ysel) then
print colour("blue","green") at(5,yoff+ydisp+a) mmtext$(a);
else
print at(5,yoff+ydisp+a) mmtext$(a);
endif
next a
print at(3,sh-3) "Move selection with CURSOR KEYS (or u and d),"
print at(3,sh-2) "Press RETURN or SPACE to choose, ESC to quit."
do // loop for keys pressed
rev=1
do // loop for blinking
k$=inkey$(0.4)
if (k$="") then
if (ysel=mmnum) then
if (rev=1) then
print colour("blue","green") at(5,yoff+mmnum+1) mmtext$(mmnum)
;
rev=0
else
print colour("yellow","red") at(5,yoff+mmnum+1) mmtext$(mmnum)
;
rev=1
endif
endif
else // key has been pressed, leave loop
break
endif
loop // loop for blinking
yalt=ysel
if (k$="up" or k$="u") then
if (ysel=1) then ysel=mmnum else ysel=ysel-1 fi
redraw():heal():continue
fi
if (k$="down" or k$="d") then
if (ysel=mmnum) then ysel=1 else ysel=ysel+1 fi
redraw():heal():continue
fi
if (k$=" " or k$="enter" or k$="right") then
on ysel gosub overview,bitmap,tetraeder,endit
goto mainloop
fi
if (k$="esc") then
endit()
fi
beep
print at(3,sh-5) "Invalid key: ",k$," "
loop // loop for keys pressed
// redraw line
sub redraw()
if (yalt=mmnum) then ydisp=1:else ydisp=0:fi
print at(5,yoff+yalt+ydisp) mmtext$(yalt);
if (ysel=mmnum) then ydisp=1:else ydisp=0:fi
print colour("blue","green") at(5,yoff+ysel+ydisp) mmtext$(ysel);
return
end sub
// erase a line
sub heal()
print at(3,sh-5) "
"
return
end sub
// Go here to exit
label endit
print at(3,sh-8) "Hope you liked it ...\n ";
exit
return
// Present a short overview
label overview
clear screen
print
print " Yabasic is a quite traditional basic: It comes with"
print " print, input, for-next-loops, goto, gosub, while and"
print " repeat. It has user defined procedures and libraries,"
print " however, it is not object oriented.\n"
print " Yabasic makes it easy to open a window, draw lines"
print " and print the resulting picture.\n"
print " Yabasic programs are interpreted and run under Unix"
print " and Windows. The Yabasic interpreter (around 200K)"
print " and any Yabasic program can be glued together to"
print " form a standalone executable.\n"
print " Yabasic is free software, i.e. subject to the"
print " MIT License.\n"
print "\n\n\n While you read this, I am calculating prime numbers,\n"
print " Press any key to return to main menu ..."
can=1
print at(6,17) "This is a prime number: "
label nextcan
can=can+2
for i=2 to sqrt(can):if (frac(can/i)=0) then goto notprime:fi:next i
print at(32,17) can;
label notprime
if (lower$(inkey$(0))<>"") then
print at(10,sh) "Wrapping around once ...";
for x=1 to sw
a$=getscreen$(0,0,1,sh-2)
b$=getscreen$(1,0,sw-1,sh-2)
putscreen b$,0,0
putscreen a$,sw-1,0
next x
sleep 2
return
fi
goto nextcan
// Show some animated bitmaps
label bitmap
clear screen
print
print "Yabasic offers some commands for drawing simple graphics."
print reverse at(5,12) " Press any key to return to main menu ... "
n=20
open window 400,400
for b=20 to 0 step -1
color 255-b*12,0,b*12
fill circle 200,200,b
next b
c$=getbit$(179,179,221,221)
for a=1 to 2000
color ran(255),ran(255),ran(255)
x=ran(500)-100:y=ran(500)-100
fill rectangle ran(500)-100,ran(500)-100,ran(500)-100,ran(500)-100
next a
x=200:y=200:phi=ran(2*pi):dx=2*sin(phi):dy=2*cos(phi)
o$=""
count=0
label pong
count=count+1
if (o$<>"") putbit o$,xo-2,yo-2
if (count>1000) then
phi=ran(2*pi):dx=2*sin(phi):dy=2*cos(phi)
sleep 2
count=0
endif
xo=x:yo=y
x=x+dx:y=y+dy
o$=getbit$(x-2,y-2,x+46,y+46)
putbit c$,x,y,"t"
if (x<0 or x>360) dx=-dx
if (y<0 or y>360) dy=-dy
if (inkey$(0)<>"") then
close window
return
endif
goto pong
return
label tetraeder
open window 400,400
clear window
clear screen
print reverse at(5,12) " Press any key to return to main menu ... "
dim opoints(4,3)
restore points
for n=1 to 4:for p=1 to 3:read opoints(n,p):next p:next n
dim triangles(4,3)
restore triangles
for n=1 to 4:for p=1 to 3:read triangles(n,p):next p:next n
phi=0:dphi=0.1:psi=0:dpsi=0.05
dim points(4,3)
r=60:g=20
dr=0.5:dg=1.2:db=3
label main
phi=phi+dphi
psi=psi+dpsi
for n=1 to 4
points(n,1)=opoints(n,1)*cos(phi)-opoints(n,2)*sin(phi)
points(n,2)=opoints(n,2)*cos(phi)+opoints(n,1)*sin(phi)
p2= points(n,2)*cos(psi)-opoints(n,3)*sin(psi)
points(n,3)=opoints(n,3)*cos(psi)+ points(n,2)*sin(psi)
points(n,2)=p2
next n
r=r+dr:if (r<0 or r>60) dr=-dr
g=g+dg:if (g<0 or g>60) dg=-dg
b=b+db:if (b<0 or b>60) db=-db
dm=dm+0.01
m=120-80*sin(dm)
for n=1 to 4
p1=triangles(n,1)
p2=triangles(n,2)
p3=triangles(n,3)
n1=points(p1,1)+points(p2,1)+points(p3,1)
n2=points(p1,2)+points(p2,2)+points(p3,2)
n3=points(p1,3)+points(p2,3)+points(p3,3)
if (n3>0) then
sp=n1*0.5-n2*0.7-n3*0.6
color 60+r+30*sp,60+g+30*sp,60+b+30*sp
fill triangle 200+m*points(p1,1),200+m*points(p1,2),200+m*points(p
2,1),200+m*points(p2,2),200+m*points(p3,1),200+m*points(p3,2)
endif
next n
if (inkey$(0.1)<>"") close window:return
clear window
goto main
label points
data -1,-1,+1, +1,-1,-1, +1,+1,+1, -1,+1,-1
label triangles
data 1,2,4, 2,3,4, 1,3,4, 1,2,3
// Data section ...
label mmdata
// Data for main menu: Number and text of entries in main menu
data 4
data " Yabasic in a nutshell "
data " Some graphics "
data " A rotating Tetraeder "
data " Exit this demo "
Chapter 10. The Copyright of yabasic
yabasic may be copied under the terms of the MIT License, which is distr
ibuted
with yabasic in the file LICENSE.
The MIT License grants extensive rights as long as you keep the copyrigh
t
notice present in most files untouched. Here is a list of things that ar
e
possible under the terms of the MIT License:
* Put yabasic on your own homepage or CD and even charge for the servi
ce of
distributing yabasic.
* Write your own yabasic-programs, pack your program and yabasic into
a
package and sell the whole thing.
* Modify yabasic and add or remove features, sell the modified version
without adding the sources.
AUTHOR
Marc Ihm, with the input and suggestions from many others.
SEE ALSO
yabasic.htm - for the hyperlinked version of the text that is presented
above.
www.yabasic.de - for further information on yabasic.
BUGS
Still some.
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