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Golang | How to find the index of rune in the string?
  • Last Updated : 28 Aug, 2019

In Go language, strings are different from other languages like Java, C++, Python, etc. It is a sequence of variable-width characters where each and every character is represented by one or more bytes using UTF-8 Encoding.
In the Go strings, you can also find the first index of the specified rune in the given string using IndexRune() function. This function returns the index of the first instance of the Unicode code point, i.e, specified rune, or -1 if the specified rune is not present in the given string. If the rune is utf8.RuneError, then it returns the first instance of any invalid UTF-8 byte sequence. It is defined under the string package so, you have to import string package in your program for accessing IndexRune function.

Syntax:

func IndexRune(str string, r rune) int

Example 1:




// Go program to illustrate how to find
// the index value of the given rune
package main
  
import (
    "fmt"
    "strings"
)
  
func main() {
  
    // Creating and Finding the first index 
    // of the rune in the given string
    // Using IndexRunefunction
    res1 := strings.IndexRune("****Welcome to GeeksforGeeks****", 60)
  
    res2 := strings.IndexRune("Learning how to trim"+
                           " a slice of bytes", 'r')
  
    res3 := strings.IndexRune("GeeksforGeeks", 'G')
  
    // Display the results
    fmt.Println("Index Value 1: ", res1)
    fmt.Println("Index Value 2: ", res2)
    fmt.Println("Index Value 3: ", res3)
  
}

Output:

Index Value 1:  -1
Index Value 2:  3
Index Value 3:  0

Example 2:




// Go program to illustrate how to find
// the index value of the given rune
package main
  
import (
    "fmt"
    "strings"
)
  
func main() {
  
    // Creating and initializing a string
    // Using shorthand declaration
    string_1 := "Welcome to GeeksforGeeks"
    string_2 := "AppleAppleAppleAppleAppleApple"
    string_3 := "%G%E%E%K%S"
  
    // Creating and initializing rune
    var r1, r2, r3 rune
    r1 = 'R'
    r2 = 'l'
    r3 = 42
  
    // Finding the first index
    // of the given rune
    // Using IndexRune function
    res1 := strings.IndexRune(string_1, r1)
    res2 := strings.IndexRune(string_2, r2)
    res3 := strings.IndexRune(string_3, r3)
  
    // Display the results
    fmt.Printf("String 1: %s , Rune 1:%q , Index Value: %d",
                                         string_1, r1, res1)
      
    fmt.Printf("\nString 2: %s , Rune 2:%q , Index Value: %d",
                                           string_2, r2, res2)
      
    fmt.Printf("\nString 3: %s , Rune 3:%q , Index Value: %d"
                                           string_3, r3, res3)
  
}

Output:

String 1: Welcome to GeeksforGeeks , Rune 1:'R' , Index Value: -1
String 2: AppleAppleAppleAppleAppleApple , Rune 2:'l' , Index Value: 3
String 3: %G%E%E%K%S , Rune 3:'*' , Index Value: -1

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