"ascii to fullwidth" convert plaintext standard chars to ｆｕｌｌｗｉｄｔｈ

atou.go

package main

import (
	"fmt"
	"os"
	"bufio"
	"strings"
)

func atofw(in string) (out string) {
	tofw := func(r rune) rune {
		switch { 
		case r >= '!' && r <= 'z':
			return r - '!' + '！'
		case r == ' ': /* fullwidth space is noncontiguous in utf8 */
			return '　';
		}
		return r
	}

	return strings.Map(tofw, in)
}

func main() {
	words := strings.Join(os.Args[1:], " ")

	/* Oneshot mode if supplied by cmdline args */
	if words != "" {
		fmt.Println(atofw(words))
		return
	}
	
	/* Otherwise loop Stdin */
	scanner := bufio.NewScanner(os.Stdin)
	for fmt.Printf("> "); scanner.Scan(); fmt.Printf("> ") {
		words := scanner.Text()
		fmt.Println(atofw(words))
	}

	return
}