Characters and runes

Go has 2 types of characters:

• byte is a 1 byte value, an alias for uint8 type
• rune is a 4 byte Unicode code-point, an alias for int32 type

Zero value of a byte and rune is 0.

Iterate over a string using bytes

s := "str"
for i := 0; i < len(s); i++ {
	c := s[i]
	fmt.Printf("Byte at index %d is '%c' (0x%x)\n", i, c, c)
}

Byte at index 0 is 's' (0x73)
Byte at index 1 is 't' (0x74)
Byte at index 2 is 'r' (0x72)

Iterate over a string using runes

s := "日本語"
for i, runeChar := range s {
	fmt.Printf("Rune at byte position %d is %#U\n", i, runeChar)
}

Rune at byte position 0 is U+65E5 '日'
Rune at byte position 3 is U+672C '本'
Rune at byte position 6 is U+8A9E '語'

A string is an array of bytes.

When iterating a string as runes we assume the string is Unicode string encoded as UTF-8.

UTF-8 is a variable-length encoding where a rune can be encoded as 1, 2, 3 or 4 bytes.

The returned index i is a byte position within the string where the rune starts. It's not a rune count.