ehlxr/gopl-zh.github.com
1
0
Fork 0
mirror of https://github.com/gopl-zh/gopl-zh.github.com.git synced 2024-12-26 23:06:20 +00:00
Code Issues Projects Releases Wiki Activity
gh-pages
gopl-zh.github.com/ch13/ch13-03.html

704 lines
34 KiB
HTML
Raw Permalink Normal View History

deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!DOCTYPE HTML>
<html lang="zh" class="sidebar-visible no-js light">
<head>
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<!-- Book generated using https://github.com/wa-lang/wabook -->
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<meta charset="UTF-8">
<title>示例: 深度相等判断 - Go语言圣经</title>
<!-- Custom HTML head -->
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<meta name="description" content="">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff" />
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<link rel="icon" href="../favicon.svg">
<link rel="shortcut icon" href="../favicon.png">
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<link rel="stylesheet" href="../static/wabook/css/variables.css">
<link rel="stylesheet" href="../static/wabook/css/general.css">
<link rel="stylesheet" href="../static/wabook/css/chrome.css">
<link rel="stylesheet" href="../static/wabook/css/print.css" media="print">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!-- Fonts -->
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<link rel="stylesheet" href="../static/wabook/FontAwesome/css/font-awesome.css">
<link rel="stylesheet" href="../static/wabook/fonts/fonts.css">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!-- Highlight.js Stylesheets -->
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<link rel="stylesheet" href="../static/wabook/highlight.css">
<link rel="stylesheet" href="../static/wabook/tomorrow-night.css">
<link rel="stylesheet" href="../static/wabook/ayu-highlight.css">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!-- Custom theme stylesheets -->
</head>
<body>
<!-- Provide site root to javascript -->
<script type="text/javascript">
var path_to_root = "../";
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
</script>
<!-- Work around some values being stored in localStorage wrapped in quotes -->
<script type="text/javascript">
try {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
var theme = localStorage.getItem('wabook-theme');
var sidebar = localStorage.getItem('wabook-sidebar');
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
if (theme.startsWith('"') && theme.endsWith('"')) {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
localStorage.setItem('wabook-theme', theme.slice(1, theme.length - 1));
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
localStorage.setItem('wabook-sidebar', sidebar.slice(1, sidebar.length - 1));
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script type="text/javascript">
var theme;
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
try { theme = localStorage.getItem('wabook-theme'); } catch(e) { }
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('no-js')
html.classList.remove('light')
html.classList.add(theme);
html.classList.add('js');
</script>
<!-- Hide / unhide sidebar before it is displayed -->
<script type="text/javascript">
var html = document.querySelector('html');
var sidebar = 'hidden';
if (document.body.clientWidth >= 1080) {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
try { sidebar = localStorage.getItem('wabook-sidebar'); } catch(e) { }
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
sidebar = sidebar || 'visible';
}
html.classList.remove('sidebar-visible');
html.classList.add("sidebar-" + sidebar);
</script>
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<div class="sidebar-scrollbox">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<ol class="chapter">
<li class="chapter-item expanded ">
<a href="../index.html" >Go语言圣经</a>
</li>
<li class="chapter-item expanded ">
<a href="../preface-zh.html" >译者序</a>
</li>
<li class="chapter-item expanded ">
<a href="../preface.html" >前言</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1.html" ><strong aria-hidden="true">1.</strong> 入门</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch1/ch1-01.html" ><strong aria-hidden="true">1.1.</strong> Hello, World</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-02.html" ><strong aria-hidden="true">1.2.</strong> 命令行参数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-03.html" ><strong aria-hidden="true">1.3.</strong> 查找重复的行</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-04.html" ><strong aria-hidden="true">1.4.</strong> GIF动画</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-05.html" ><strong aria-hidden="true">1.5.</strong> 获取URL</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-06.html" ><strong aria-hidden="true">1.6.</strong> 并发获取多个URL</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-07.html" ><strong aria-hidden="true">1.7.</strong> Web服务</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-08.html" ><strong aria-hidden="true">1.8.</strong> 本章要点</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch2/ch2.html" ><strong aria-hidden="true">2.</strong> 程序结构</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch2/ch2-01.html" ><strong aria-hidden="true">2.1.</strong> 命名</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-02.html" ><strong aria-hidden="true">2.2.</strong> 声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-03.html" ><strong aria-hidden="true">2.3.</strong> 变量</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-04.html" ><strong aria-hidden="true">2.4.</strong> 赋值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-05.html" ><strong aria-hidden="true">2.5.</strong> 类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-06.html" ><strong aria-hidden="true">2.6.</strong> 包和文件</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-07.html" ><strong aria-hidden="true">2.7.</strong> 作用域</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch3/ch3.html" ><strong aria-hidden="true">3.</strong> 基础数据类型</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch3/ch3-01.html" ><strong aria-hidden="true">3.1.</strong> 整型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-02.html" ><strong aria-hidden="true">3.2.</strong> 浮点数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-03.html" ><strong aria-hidden="true">3.3.</strong> 复数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-04.html" ><strong aria-hidden="true">3.4.</strong> 布尔型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-05.html" ><strong aria-hidden="true">3.5.</strong> 字符串</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-06.html" ><strong aria-hidden="true">3.6.</strong> 常量</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch4/ch4.html" ><strong aria-hidden="true">4.</strong> 复合数据类型</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch4/ch4-01.html" ><strong aria-hidden="true">4.1.</strong> 数组</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-02.html" ><strong aria-hidden="true">4.2.</strong> Slice</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-03.html" ><strong aria-hidden="true">4.3.</strong> Map</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-04.html" ><strong aria-hidden="true">4.4.</strong> 结构体</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-05.html" ><strong aria-hidden="true">4.5.</strong> JSON</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-06.html" ><strong aria-hidden="true">4.6.</strong> 文本和HTML模板</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch5/ch5.html" ><strong aria-hidden="true">5.</strong> 函数</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch5/ch5-01.html" ><strong aria-hidden="true">5.1.</strong> 函数声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-02.html" ><strong aria-hidden="true">5.2.</strong> 递归</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-03.html" ><strong aria-hidden="true">5.3.</strong> 多返回值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-04.html" ><strong aria-hidden="true">5.4.</strong> 错误</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-05.html" ><strong aria-hidden="true">5.5.</strong> 函数值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-06.html" ><strong aria-hidden="true">5.6.</strong> 匿名函数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-07.html" ><strong aria-hidden="true">5.7.</strong> 可变参数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-08.html" ><strong aria-hidden="true">5.8.</strong> Deferred函数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-09.html" ><strong aria-hidden="true">5.9.</strong> Panic异常</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-10.html" ><strong aria-hidden="true">5.10.</strong> Recover捕获异常</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch6/ch6.html" ><strong aria-hidden="true">6.</strong> 方法</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch6/ch6-01.html" ><strong aria-hidden="true">6.1.</strong> 方法声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-02.html" ><strong aria-hidden="true">6.2.</strong> 基于指针对象的方法</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-03.html" ><strong aria-hidden="true">6.3.</strong> 通过嵌入结构体来扩展类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-04.html" ><strong aria-hidden="true">6.4.</strong> 方法值和方法表达式</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-05.html" ><strong aria-hidden="true">6.5.</strong> 示例: Bit数组</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-06.html" ><strong aria-hidden="true">6.6.</strong> 封装</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch7/ch7.html" ><strong aria-hidden="true">7.</strong> 接口</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch7/ch7-01.html" ><strong aria-hidden="true">7.1.</strong> 接口是合约</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-02.html" ><strong aria-hidden="true">7.2.</strong> 接口类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-03.html" ><strong aria-hidden="true">7.3.</strong> 实现接口的条件</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-04.html" ><strong aria-hidden="true">7.4.</strong> flag.Value接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-05.html" ><strong aria-hidden="true">7.5.</strong> 接口值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-06.html" ><strong aria-hidden="true">7.6.</strong> sort.Interface接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-07.html" ><strong aria-hidden="true">7.7.</strong> http.Handler接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-08.html" ><strong aria-hidden="true">7.8.</strong> error接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-09.html" ><strong aria-hidden="true">7.9.</strong> 示例: 表达式求值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-10.html" ><strong aria-hidden="true">7.10.</strong> 类型断言</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-11.html" ><strong aria-hidden="true">7.11.</strong> 基于类型断言识别错误类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-12.html" ><strong aria-hidden="true">7.12.</strong> 通过类型断言查询接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-13.html" ><strong aria-hidden="true">7.13.</strong> 类型分支</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-14.html" ><strong aria-hidden="true">7.14.</strong> 示例: 基于标记的XML解码</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-15.html" ><strong aria-hidden="true">7.15.</strong> 补充几点</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch8/ch8.html" ><strong aria-hidden="true">8.</strong> Goroutines和Channels</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch8/ch8-01.html" ><strong aria-hidden="true">8.1.</strong> Goroutines</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-02.html" ><strong aria-hidden="true">8.2.</strong> 示例: 并发的Clock服务</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-03.html" ><strong aria-hidden="true">8.3.</strong> 示例: 并发的Echo服务</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-04.html" ><strong aria-hidden="true">8.4.</strong> Channels</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-05.html" ><strong aria-hidden="true">8.5.</strong> 并发的循环</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-06.html" ><strong aria-hidden="true">8.6.</strong> 示例: 并发的Web爬虫</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-07.html" ><strong aria-hidden="true">8.7.</strong> 基于select的多路复用</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-08.html" ><strong aria-hidden="true">8.8.</strong> 示例: 并发的目录遍历</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-09.html" ><strong aria-hidden="true">8.9.</strong> 并发的退出</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-10.html" ><strong aria-hidden="true">8.10.</strong> 示例: 聊天服务</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch9/ch9.html" ><strong aria-hidden="true">9.</strong> 基于共享变量的并发</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch9/ch9-01.html" ><strong aria-hidden="true">9.1.</strong> 竞争条件</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-02.html" ><strong aria-hidden="true">9.2.</strong> sync.Mutex互斥锁</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-03.html" ><strong aria-hidden="true">9.3.</strong> sync.RWMutex读写锁</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-04.html" ><strong aria-hidden="true">9.4.</strong> 内存同步</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-05.html" ><strong aria-hidden="true">9.5.</strong> sync.Once惰性初始化</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-06.html" ><strong aria-hidden="true">9.6.</strong> 竞争条件检测</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-07.html" ><strong aria-hidden="true">9.7.</strong> 示例: 并发的非阻塞缓存</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-08.html" ><strong aria-hidden="true">9.8.</strong> Goroutines和线程</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch10/ch10.html" ><strong aria-hidden="true">10.</strong> 包和工具</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch10/ch10-01.html" ><strong aria-hidden="true">10.1.</strong> 包简介</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-02.html" ><strong aria-hidden="true">10.2.</strong> 导入路径</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-03.html" ><strong aria-hidden="true">10.3.</strong> 包声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-04.html" ><strong aria-hidden="true">10.4.</strong> 导入声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-05.html" ><strong aria-hidden="true">10.5.</strong> 包的匿名导入</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-06.html" ><strong aria-hidden="true">10.6.</strong> 包和命名</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-07.html" ><strong aria-hidden="true">10.7.</strong> 工具</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch11/ch11.html" ><strong aria-hidden="true">11.</strong> 测试</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch11/ch11-01.html" ><strong aria-hidden="true">11.1.</strong> go test</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-02.html" ><strong aria-hidden="true">11.2.</strong> 测试函数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-03.html" ><strong aria-hidden="true">11.3.</strong> 测试覆盖率</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-04.html" ><strong aria-hidden="true">11.4.</strong> 基准测试</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-05.html" ><strong aria-hidden="true">11.5.</strong> 剖析</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-06.html" ><strong aria-hidden="true">11.6.</strong> 示例函数</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch12/ch12.html" ><strong aria-hidden="true">12.</strong> 反射</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch12/ch12-01.html" ><strong aria-hidden="true">12.1.</strong> 为何需要反射?</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-02.html" ><strong aria-hidden="true">12.2.</strong> reflect.Type和reflect.Value</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-03.html" ><strong aria-hidden="true">12.3.</strong> Display递归打印</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-04.html" ><strong aria-hidden="true">12.4.</strong> 示例: 编码S表达式</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-05.html" ><strong aria-hidden="true">12.5.</strong> 通过reflect.Value修改值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-06.html" ><strong aria-hidden="true">12.6.</strong> 示例: 解码S表达式</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-07.html" ><strong aria-hidden="true">12.7.</strong> 获取结构体字段标签</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-08.html" ><strong aria-hidden="true">12.8.</strong> 显示一个类型的方法集</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-09.html" ><strong aria-hidden="true">12.9.</strong> 几点忠告</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch13/ch13.html" ><strong aria-hidden="true">13.</strong> 底层编程</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch13/ch13-01.html" ><strong aria-hidden="true">13.1.</strong> unsafe.Sizeof, Alignof 和 Offsetof</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-02.html" ><strong aria-hidden="true">13.2.</strong> unsafe.Pointer</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-03.html" class="active"><strong aria-hidden="true">13.3.</strong> 示例: 深度相等判断</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-04.html" ><strong aria-hidden="true">13.4.</strong> 通过cgo调用C代码</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-05.html" ><strong aria-hidden="true">13.5.</strong> 几点忠告</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../appendix/appendix.html" ><strong aria-hidden="true">14.</strong> 附录</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../appendix/appendix-a-errata.html" ><strong aria-hidden="true">14.1.</strong> 附录A：原文勘误</a>
</li>
<li class="chapter-item expanded ">
<a href="../appendix/appendix-b-author.html" ><strong aria-hidden="true">14.2.</strong> 附录B：作者译者</a>
</li>
<li class="chapter-item expanded ">
<a href="../appendix/appendix-c-cpoyright.html" ><strong aria-hidden="true">14.3.</strong> 附录C：译文授权</a>
</li>
<li class="chapter-item expanded ">
<a href="../appendix/appendix-d-translations.html" ><strong aria-hidden="true">14.4.</strong> 附录D：其它语言</a>
</li>
</ol>
</ol>
</div>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
</nav>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar-hover-placeholder"></div>
<div id="menu-bar" class="menu-bar sticky bordered">
<div class="left-buttons">
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</button>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
</div>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<h1 class="menu-title"><a href="../index.html">Go语言圣经</a></h1>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<div class="right-buttons">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a href="https://github.com/gopl-zh/gopl-zh.github.com" title="Git repository" aria-label="Git repository">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i id="git-repository-button" class="fa fa-github"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a href="https://github.com/gopl-zh/gopl-zh.github.com/edit/master/ch13/ch13-03.md" title="Suggest an edit" aria-label="Suggest an edit">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i id="git-edit-button" class="fa fa-edit"></i>
</a>
</div>
</div>
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
<script type="text/javascript">
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
</script>
<div id="content" class="content">
<!-- Page table of contents -->
<div class="sidetoc"><nav class="pagetoc"></nav></div>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<main>
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<ul dir="auto"><li><em>凹语言(Go实现, 面向WASM设计): <a href="https://github.com/wa-lang/wa">https://github.com/wa-lang/wa</a></em></li><li><em>WaBook(Go语言实现的MD电子书构建工具): <a href="https://github.com/wa-lang/wabook">https://github.com/wa-lang/wabook</a></em></li></ul><hr>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<h2>13.3. 示例: 深度相等判断</h2>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<p>来自reflect包的DeepEqual函数可以对两个值进行深度相等判断。DeepEqual函数使用内建的==比较操作符对基础类型进行相等判断，对于复合类型则递归该变量的每个基础类型然后做类似的比较判断。因为它可以工作在任意的类型上，甚至对于一些不支持==操作运算符的类型也可以工作，因此在一些测试代码中广泛地使用该函数。比如下面的代码是用DeepEqual函数比较两个字符串slice是否相等。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code class="language-Go">func TestSplit(t *testing.T) {
got := strings.Split(&quot;a:b:c&quot;, &quot;:&quot;)
want := []string{&quot;a&quot;, &quot;b&quot;, &quot;c&quot;};
if !reflect.DeepEqual(got, want) { /* ... */ }
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>尽管DeepEqual函数很方便，而且可以支持任意的数据类型，但是它也有不足之处。例如，它将一个nil值的map和非nil值但是空的map视作不相等，同样nil值的slice 和非nil但是空的slice也视作不相等。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code class="language-Go">var a, b []string = nil, []string{}
fmt.Println(reflect.DeepEqual(a, b)) // &quot;false&quot;
var c, d map[string]int = nil, make(map[string]int)
fmt.Println(reflect.DeepEqual(c, d)) // &quot;false&quot;
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>我们希望在这里实现一个自己的Equal函数，用于比较类型的值。和DeepEqual函数类似的地方是它也是基于slice和map的每个元素进行递归比较，不同之处是它将nil值的slice（map类似）和非nil值但是空的slice视作相等的值。基础部分的比较可以基于reflect包完成，和12.3章的Display函数的实现方法类似。同样，我们也定义了一个内部函数equal，用于内部的递归比较。读者目前不用关心seen参数的具体含义。对于每一对需要比较的x和y，equal函数首先检测它们是否都有效（或都无效），然后检测它们是否是相同的类型。剩下的部分是一个巨大的switch分支，用于相同基础类型的元素比较。因为页面空间的限制，我们省略了一些相似的分支。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<p><!-- raw HTML omitted --><!-- raw HTML omitted -->gopl.io/ch13/equal<!-- raw HTML omitted --><!-- raw HTML omitted --></p>
<pre><code class="language-Go">func equal(x, y reflect.Value, seen map[comparison]bool) bool {
if !x.IsValid() || !y.IsValid() {
return x.IsValid() == y.IsValid()
}
if x.Type() != y.Type() {
return false
}
// ...cycle check omitted (shown later)...
switch x.Kind() {
case reflect.Bool:
return x.Bool() == y.Bool()
case reflect.String:
return x.String() == y.String()
// ...numeric cases omitted for brevity...
case reflect.Chan, reflect.UnsafePointer, reflect.Func:
return x.Pointer() == y.Pointer()
case reflect.Ptr, reflect.Interface:
return equal(x.Elem(), y.Elem(), seen)
case reflect.Array, reflect.Slice:
if x.Len() != y.Len() {
return false
}
for i := 0; i &lt; x.Len(); i++ {
if !equal(x.Index(i), y.Index(i), seen) {
return false
}
}
return true
// ...struct and map cases omitted for brevity...
}
panic(&quot;unreachable&quot;)
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>和前面的建议一样，我们并不公开reflect包相关的接口，所以导出的函数需要在内部自己将变量转为reflect.Value类型。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code class="language-Go">// Equal reports whether x and y are deeply equal.
func Equal(x, y interface{}) bool {
seen := make(map[comparison]bool)
return equal(reflect.ValueOf(x), reflect.ValueOf(y), seen)
}
type comparison struct {
x, y unsafe.Pointer
t reflect.Type
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>为了确保算法对于有环的数据结构也能正常退出，我们必须记录每次已经比较的变量，从而避免进入第二次的比较。Equal函数分配了一组用于比较的结构体，包含每对比较对象的地址（unsafe.Pointer形式保存）和类型。我们要记录类型的原因是，有些不同的变量可能对应相同的地址。例如，如果x和y都是数组类型，那么x和x[0]将对应相同的地址，y和y[0]也是对应相同的地址，这可以用于区分x与y之间的比较或x[0]与y[0]之间的比较是否进行过了。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code class="language-Go">// cycle check
if x.CanAddr() &amp;&amp; y.CanAddr() {
xptr := unsafe.Pointer(x.UnsafeAddr())
yptr := unsafe.Pointer(y.UnsafeAddr())
if xptr == yptr {
return true // identical references
}
c := comparison{xptr, yptr, x.Type()}
if seen[c] {
return true // already seen
}
seen[c] = true
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>这是Equal函数用法的例子:</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code class="language-Go">fmt.Println(Equal([]int{1, 2, 3}, []int{1, 2, 3})) // &quot;true&quot;
fmt.Println(Equal([]string{&quot;foo&quot;}, []string{&quot;bar&quot;})) // &quot;false&quot;
fmt.Println(Equal([]string(nil), []string{})) // &quot;true&quot;
fmt.Println(Equal(map[string]int(nil), map[string]int{})) // &quot;true&quot;
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>Equal函数甚至可以处理类似12.3章中导致Display陷入死循环的带有环的数据。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code class="language-Go">// Circular linked lists a -&gt; b -&gt; a and c -&gt; c.
type link struct {
value string
tail *link
}
a, b, c := &amp;link{value: &quot;a&quot;}, &amp;link{value: &quot;b&quot;}, &amp;link{value: &quot;c&quot;}
a.tail, b.tail, c.tail = b, a, c
fmt.Println(Equal(a, a)) // &quot;true&quot;
fmt.Println(Equal(b, b)) // &quot;true&quot;
fmt.Println(Equal(c, c)) // &quot;true&quot;
fmt.Println(Equal(a, b)) // &quot;false&quot;
fmt.Println(Equal(a, c)) // &quot;false&quot;
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p><strong>练习 13.1：</strong> 定义一个深比较函数，对于十亿以内的数字比较，忽略类型差异。</p>
<p><strong>练习 13.2：</strong> 编写一个函数，报告其参数是否为循环数据结构。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<hr><table><tr><td><img width="222px" src="https://chai2010.cn/advanced-go-programming-book/css.png"></td><td><img width="222px" src="https://chai2010.cn/advanced-go-programming-book/cch.png"></td></tr></table>
<div id="giscus-container"></div>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<footer class="page-footer">
<span>© 2015-2016 | <a href="https://github.com/gopl-zh"> Go语言圣经中文版</a>, 仅学习交流使用</span>
</footer>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a rel="prev" href="../ch13/ch13-02.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-left"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<!-- ../ch13/ch13-04.html -->
<a rel="next" href="../ch13/ch13-04.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-right"></i>
</a>
<div style="clear: both"></div>
</nav>
</div>
</div>
<nav class="nav-wide-wrapper" aria-label="Page navigation">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a rel="prev" href="../ch13/ch13-02.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-left"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a rel="next" href="../ch13/ch13-04.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-right"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
</nav>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</div>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<script type="text/javascript">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
window.playground_copyable = true;
</script>
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<script src="../static/wabook/mark.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../static/wabook/clipboard.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../static/wabook/highlight.js" type="text/javascript" charset="utf-8"></script>
<script src="../static/wabook/book.js" type="text/javascript" charset="utf-8"></script>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<script type="text/javascript" charset="utf-8">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
var pagePath = "ch13/ch13-03.md"
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</script>
<!-- Custom JS scripts -->
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<script src="../static/wabook/giscus.js" type="text/javascript" charset="utf-8"></script>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</body>
</html>
Reference in New Issue Copy Permalink