Rune. In Go a rune is a Unicode code point. Strings are encoded in UTF-8, and this means each character may be more than one byte—and the rune handles this. Rune is a 4-byte value like int32.
Some string methods (like those found in the "strings" package) require rune arguments. And the for-range loop over a string returns a rune as the second output value.
Example. This program uses runes in a variety of ways. It uses a rune as an argument, and also creates various local variables that have the rune type.
Step 1 We create a local variable of rune type by specifying the value "x" in single quotes. We can pass this to a method like ContainsRune.
Step 4 A rune is an alias for the int32 type, so it is safe to convert back and forth from int32 with this type.
package main
import (
"fmt""strings"
)
func TestRune(x rune) bool {
// Step 3: test a rune value.
if x == 'c' {
return true
}
return false
}
func main() {
// Step 1: use rune literal, and pass rune literal to strings.ContainsRune.
value := 'x'
if strings.ContainsRune("abc_x", value) {
fmt.Println("Contains rune", value)
}
// Step 2: use for-range loop over string, and use the second value which is a rune.
word := "cat"
for i, letter := range word {
fmt.Println(i, letter, TestRune(letter))
}
// Step 4: convert from int32 to rune.
test := int32(100)
testRune := rune(test)
fmt.Println(test, testRune)
}Contains rune 120
0 99 true
1 97 false
2 116 false
100 100
Summary. Runes are important as they can store values beyond ASCII—we can have accents and other characters. Constructs like the for-range loop correctly handle these cases.
Dot Net Perls is a collection of pages with code examples, which are updated to stay current. Programming is an art, and it can be learned from examples.
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