strings.IndexFunc() Function in Golang With Examples

strings.IndexFunc() Function in Golang is used to returns the index into s of the first Unicode code point satisfying f(c), or -1 if none do. Syntax:

func IndexFunc(str string, f func(rune) bool) int

Here, str is string which may contain Unicode code point and f is func which validates the Unicode point. Return Value: It returns the index of the first Unicode code point satisfying func. Example 1:

// Golang program to show the usage
// of strings.IndexFunc() Function
package main

// importing fmt, unicode and strings
import (
 "fmt"
 "strings"
 "unicode"
)

func main() {

 // func f which validates the Greek 
 // Unicode character in the string
 f := func(c rune) bool {
 return unicode.Is(unicode.Greek, c)
 }
 
 // using the function
 fmt.Println(strings.IndexFunc("Hello Geeks!α", f)) 
}

Output:

13

Example 2: Output:

-1