Golang string comparison

golang String comparison

String comparison , You can use it directly == Compare , It can also be used strings.Compare Compare

go There are three ways to compare strings in ：

• == Compare
• strings.Compare Compare
• strings.EquslFold Compare

####  Code example 
```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"))

The above code execution results are as follows ：

true
false
-1
0
true

Compare and EqualFold difference

• EqualFold Is the more UTF-8 Whether the codes are equal in lowercase , Case insensitive

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

• It should be noted that Compare Functions are case sensitive , == Faster execution

/ 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

Ignore case comparison

Sometimes you have to ignore the case comparison , have access to strings.EqualFold Compare strings for equality

The source code to achieve

// 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
}

Through the source code, you can see if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' You can see the case insensitive implementation .

Look at a complete test code ：

// 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"))
}

Execution structure

true
true

Reference material

• https://www.geeksforgeeks.org/strings-equalfold-function-in-golang-with-examples/
• https://cloud.tencent.com/developer/article/1651885