LEX Code that accepts the string with 0 only

In this article, we will discuss the overview of the LEX Code that accepts the string with 0 only. And will implement with LEX code also, we will understand the approach. Let's discuss it one by one.

Problem Overview :
LEX Code that accepts the string with 0 only.

Example -

Input : 00
Output : Accepted

Input : 1000
Output : Invalid

Input : 23ab
Output : Invalid

Input : ab345
Output : Invalid

Input : 00000
Output : Accepted

Approach :
LEX provides us with an INITIAL state by default. So to make a DFA, use this as the initial state of the DFA. We define two more states: A, and DEAD, where the DEAD state would be used if encountering a wrong or invalid input. When the user inputs an invalid character, move to DEAD state, and then print “Invalid”. If the input string ends at A then display the message “Accepted”. Else if the input string ends at state INITIAL then displays the message “Not Accepted”.

Note -
To compile the lex program we need to have a Unix system that has flex installed into it. Then we need to save the file with the .l extension.

Example :

filename.l

Then after saving the program closes the lex file and then open the terminal and write the following commands as follows.

lex filename.l
cc lex.yy.c
./a.out

LEX Code :

Output :