为什么fmt.Printf（“％x”，'ᚵ'）〜> 16b5，而fmt.Printf（“％x”，“ᚵ”）〜> e19ab5？

Question

package main

import (
    "fmt"
)

func main() {
    fmt.Printf("%c, %x, %x", 'ᚵ', 'ᚵ', "ᚵ")
}

Outputs:

ᚵ, 16b5, e19ab5

https://play.golang.org/p/_Bs7JcdOfO

Answer 1

Because each does a different thing. Both format the argument as a hexadecimal number, but each views the argument differently.

fmt.Printf("%x", 'ᚵ') prints a single unicode character (a rune, if you will), as a 32 bit integer (int32).

fmt.Printf("%x", "ᚵ") prints a string (individual bytes of a string) as 8 bit integers (uint8). The rune is encoded on three bytes when utf-8 encoding is used. That is a reason why there is six hexadecimal digits (two for each byte).

To study printing of a string in detail, start at function fmtString in file fmt/print.go.

func (p *pp) fmtString(v string, verb rune) {