How to compare strings in go language-Golang-php.cn

<blockquote><p>Comparison method: 1. Directly use the "==" operator to compare, the syntax is "str1 == str2", this method is case-sensitive. 2. Compare using the Compare() function of the strings package, with the syntax "strings.Compare(a,b)"; the return value is int type, 0 means the two numbers are equal, 1 means a is greater than b, and "-1" means a is less than b. . 3. Use the EqualFold() comparison of the strings package, with the syntax "strings.EqualFold(a,b)". </p></blockquote> <p><img src="https://img.php.cn/upload/article/000/000/024/63c224119dee6813.jpg" alt="How to compare strings in go language" ></p> <p>The operating environment of this tutorial: Windows 7 system, GO version 1.18, Dell G3 computer. </p> <h2><strong>Go language string comparison methods</strong></h2> <p>There are three string comparison methods in go language: </p> <ul class="ul-level-0"> <li> <code> ==</code> Direct comparison, case sensitive</li> <li> <code>strings.Compare(a,b)</code> The return value of this function is int, 0 means the two numbers are equal, 1 means a>b, -1 means a<b. case-sensitive><li> <code>strings.EqualFold(a,b)</code> Directly returns whether they are equal, not case-sensitive. </li></b.> </li> </ul> <p>Examples are as follows:<span style="background-color: rgb(248, 248, 248);">// 1-Use equal sign comparison - distinguish large messages</span></p> <div class="developer-code-block"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">func Equal(s1, s2 string) bool { return s1 == s2 } // 2-使用 compare 比较——区分大小写 func Compare(s1, s2 string) bool { return strings.Compare(s1, s2) == 0 // } //3-EqualFold 比较——不区分大小写. case-fold 即大小写同一处理 func EqualFold(s1, s2 string) bool { return strings.EqualFold(s1, s2) } // 使用等号比较——忽略大小写 func Equal2(s1, s2 string) bool { return strings.ToLower(s1) == strings.ToLower(s2) } // 使用 compare 比较——不区分大小写 func Compare2(s1, s2 string) bool { return strings.Compare(strings.ToLower(s1), strings.ToLower(s2)) == 0 } func StringCompareTest() { fmt.Println("== 区分大小写", Equal("go", "Go")) //false fmt.Println("== 忽略大小写",Equal2("go", "Go")) //true fmt.Println("compare 区分大小写",Compare("go", "Go")) //false fmt.Println("compare 忽略大小写",Compare2("go", "Go")) //true fmt.Println("EqualFold 忽略大小写",EqualFold("go", "Go")) // true }</pre><div class="contentsignin">Copy after login</div></div></div><h2><strong>Performance comparison</strong></h2><p>The following code uses Benchmark to do a simple performance comparison. The directory structure of the test project is: </p><p><img src="https://img.php.cn/upload/image/916/800/564/167367265364778How to compare strings in go language" title="167367265364778How to compare strings in go language" alt="How to compare strings in go language"/></p><p>Detailed code: </p><div class="developer-code-block"> <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">package test import ( "../str" "testing" ) func BenchmarkStrEqual(b *testing.B) { for i := 0; i < b.N; i++ { str.Equal("go", "Go") } } func BenchmarkStrEqual2(b *testing.B) { for i := 0; i < b.N; i++ { str.Equal2("go", "Go") } } func BenchmarkStrCompare(b *testing.B) { for i := 0; i < b.N; i++ { str.Compare("go", "Go") } } func BenchmarkStrCompare2(b *testing.B) { for i := 0; i < b.N; i++ { str.Compare2("go", "Go") } } func BenchmarkStrEqualFold(b *testing.B) { for i := 0; i < b.N; i++ { str.EqualFold("go", "Go") } }</pre><div class="contentsignin">Copy after login</div></div></div><p>The test results are as follows:</p><p><img src="https://img.php.cn/upload/image/725/103/124/1673672666716944.png" title="1673672666716944.png" alt="How to compare strings in go language"/></p><p>As can be seen from the above figure, the most efficient one is ==</p><h2><strong>The source code is simple Analysis</strong></h2><h4 id="3.1-strings.Compare" name="3.1-strings.Compare"><strong>1, strings.Compare</strong></h4><div class="developer-code-block"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">package strings // Compare returns an integer comparing two strings lexicographically. // The result will be 0 if a==b, -1 if a < b, and +1 if a > b. // // 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 { // NOTE(rsc): This function does NOT call the runtime cmpstring function, // because we do not want to provide any performance justification for // using strings.Compare. Basically no one should use strings.Compare. // As the comment above says, it is here only for symmetry with package bytes. // If performance is important, the compiler should be changed to recognize // the pattern so that all code doing three-way comparisons, not just code // using strings.Compare, can benefit. if a == b { return 0 } if a < b { return -1 } return +1 }</pre><div class="contentsignin">Copy after login</div></div></div><p>As shown above, we found that Compare also calls <code>= internally =</code>, and the comment of this function also says that this function is only for symmetry with package bytes. And it is recommended that we use <code>==</code> and <code>></code>, <code><</code> directly. </p><h4 id="3.2-strings.EqualFold" name="3.2-strings.EqualFold"><strong>2, strings.EqualFold</strong></h4><div class="developer-code-block"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">// 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 }</pre><div class="contentsignin">Copy after login</div></div></div> <p>This function performs a series of operations to convert two strings into <code>utf -8</code> Strings are compared, ignoring case when comparing. </p> <h2><strong>Summary</strong></h2> <p>Through the above simple summary and analysis, we found that for string comparison, it is better to directly use the ==, >, </p> <p>【Related recommendations: <a href="http://www.php.cn/course/list/44.html" target="_blank">Go video tutorial</a>, <a href="https://www.php.cn/course.html" target="_blank" textvalue="编程教学">Programming teaching</a>】</p>

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