需要使用“ exp / utf8string”将代码转换为更高的标准库代码

Question

I am trying to ran an example from The Go Programming Language Phrasebook - the book was written in 2012, based on Go 1.0 . The example uses the exp/utf8string package, which has now become unicode/utf8. I am currently using Go 1.2.1 and code listed below will not compile as is, since the exp/utf8string package is now defunct:

package main
import "strings"
import "unicode"
import "exp/utf8string"
import "fmt"

func main()
{
    str := "\tthe important rôles of utf8 text
"
    str = strings.TrimFunc(str, unicode.IsSpace)

    // The wrong way
    fmt.Printf("%s
", str[0:len(str)/2])
    // The right way
    u8 := utf8string.NewString(str)
    FirstHalf := u8.Slice(0, u8.RuneCount()/2)
    fmt.Printf("%s
", FirstHalf)

}

I am a still a GoLang newbie, so I'm not sure how the older experimental packages were integrated into the standard library. I did a bit of research and found that utf8string.NewString(str) is nowexpvar.NewString(str), so I changed my imports to

expvar
unicode

and modified the code appropriately to call expvar.NewString(str),but I'm still getting two errors:

u8.Slice undefined (type *expvar.String has no field or method Slice)
u8.RuneCount undefined (type *expvar.String has no field or method RuneCount)

I've tried a few different ways but can't seem to get it to work.

How should this example code be written for GoLang 1.2.1?

Answer 1

Install package utf8string:

$ go get -v code.google.com/p/go.exp/utf8string
code.google.com/p/go.exp (download)
code.google.com/p/go.exp/utf8string
$

Fix the program:

package main

import (
    "fmt"
    "strings"
    "unicode"

    "code.google.com/p/go.exp/utf8string"
)

func main() {
    str := "\tthe important rôles of utf8 text
"
    str = strings.TrimFunc(str, unicode.IsSpace)

    // The wrong way
    fmt.Printf("%s
", str[0:len(str)/2])
    // The right way
    u8 := utf8string.NewString(str)
    FirstHalf := u8.Slice(0, u8.RuneCount()/2)
    fmt.Printf("%s
", FirstHalf)
}

Output:

the important r
the important rô

Revising the program to only use Go 1.2.1 standard packages:

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "\tthe important rôles of utf8 text
"
    str = strings.TrimSpace(str)

    // The wrong way
    fmt.Printf("%s
", str[0:len(str)/2])
    // The right way
    r := []rune(str)
    FirstHalf := string(r[:len(r)/2])
    fmt.Printf("%s
", FirstHalf)
}

Output:

the important r
the important rô