简单介绍Go 字符串比较的实现示例

字符串比较， 可以直接使用 == 进行比较， 也可用用 strings.Compare 比较

go 中字符串比较有三种方式：

== 比较

strings.Compare 比较

strings.EquslFold 比较

#### 代码示例
```go
fmt.Println("go"=="go")
fmt.Println("GO"=="go")
 
fmt.Println(strings.Compare("GO","go"))
fmt.Println(strings.Compare("go","go"))
 
fmt.Println(strings.EqualFold("GO","go"))

上述代码执行结果如下：

true
false
-1
0
true

EqualFold 是比较UTF-8编码在小写的条件下是否相等，不区分大小写

// EqualFold reports whether s and t, interpreted as UTF-8 strings, // are equal under Unicode case-folding. func EqualFold(s, t string) bool

要注意的是 Compare 函数是区分大小写的， == 速度执行更快

// Compare is included only for symmetry with package bytes. // It is usually clearer and always faster to use the built-in // string comparison operators ==, <,>, and so on. func Compare(a, b string) int

有时候要忽略大小写比较, 可以使用strings.EqualFold 字符串比较是否相等

源码实现

// EqualFold reports whether s and t, interpreted as UTF-8 strings,
// are equal under Unicode case-folding, which is a more general
// form of case-insensitivity.
func EqualFold(s, t string) bool {
    for s != "" && t != "" {
        // Extract first rune from each string.
        var sr, tr rune
        if s[0] < utf8.runeself="" {="" sr,="" s="rune(s[0])," s[1:]="" }="" else="" {="" r,="" size="" :="utf8.DecodeRuneInString(s)" sr,="" s="r," s[size:]="" }="" if="" t[0]="">< utf8.runeself="" {="" tr,="" t="rune(t[0])," t[1:]="" }="" else="" {="" r,="" size="" :="utf8.DecodeRuneInString(t)" tr,="" t="r," t[size:]="" }="" if="" they="" match,="" keep="" going;="" if="" not,="" return="" false.="" easy="" case.="" if="" tr="=" sr="" {="" continue="" }="" make="" sr="">< tr="" to="" simplify="" what="" follows.="" if="" tr="">< sr="" {="" tr,="" sr="sr," tr="" }="" fast="" check="" for="" ascii.="" if="" tr="">< utf8.runeself="" {="" ascii="" only,="" sr/tr="" must="" be="" upper/lower="" case="" if="" 'a'=""><= sr="" &&="" sr=""><= 'z'="" &&="" tr="=" sr+'a'-'a'="" {="" continue="" }="" return="" false="" }="" general="" case.="" simplefold(x)="" returns="" the="" next="" equivalent="" rune=""> x
        // or wraps around to smaller values.
        r := unicode.SimpleFold(sr)
        for r != sr && r < tr="" {="" r="unicode.SimpleFold(r)" }="" if="" r="=" tr="" {="" continue="" }="" return="" false="" }="" one="" string="" is="" empty.="" are="" both?="" return="" s="=" t="">

通过源码可看到 if 'A' <= sr="" &&="" sr=""><= 'z'="" &&="" tr="=" sr+'a'-'a'="" 可以看到不区分大小写的实现。="" 看个完整测试代码：="">

// Golang program to illustrate the
// strings.EqualFold() Function
package main
 
// importing fmt and strings
import (
    "fmt"
    "strings"
)
 
// calling main method
func main() {
    // case insensitive comparing and returns true.
    fmt.Println(strings.EqualFold("Geeks", "Geeks"))
 
    // case insensitive comparing and returns true.
    fmt.Println(strings.EqualFold("computerscience", "computerscience"))
}

执行结构
true
true

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