2195 lines
71 KiB
HTML
2195 lines
71 KiB
HTML
<!DOCTYPE HTML>
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<html lang="zh-tw" >
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<head>
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<meta charset="UTF-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge" />
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<title>示例: 編碼S表達式 | Go语言圣经</title>
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<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
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<meta name="description" content="">
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<meta name="generator" content="GitBook 2.6.6">
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<meta name="HandheldFriendly" content="true"/>
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<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
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<meta name="apple-mobile-web-app-capable" content="yes">
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<meta name="apple-mobile-web-app-status-bar-style" content="black">
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<link rel="apple-touch-icon-precomposed" sizes="152x152" href="../gitbook/images/apple-touch-icon-precomposed-152.png">
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<link rel="shortcut icon" href="../gitbook/images/favicon.ico" type="image/x-icon">
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<link rel="stylesheet" href="../gitbook/style.css">
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<link rel="stylesheet" href="../gitbook/plugins/gitbook-plugin-katex/katex.min.css">
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<link rel="stylesheet" href="../gitbook/plugins/gitbook-plugin-highlight/website.css">
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<link rel="stylesheet" href="../gitbook/plugins/gitbook-plugin-fontsettings/website.css">
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<link rel="next" href="../ch12/ch12-05.html" />
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<link rel="prev" href="../ch12/ch12-03.html" />
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</head>
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<body>
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<div class="book"
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data-level="12.4"
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data-chapter-title="示例: 編碼S表達式"
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data-filepath="ch12/ch12-04.md"
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data-basepath=".."
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data-revision="Sat Jan 02 2016 16:00:23 GMT+0800 (中国标准时间)"
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data-innerlanguage="">
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<div class="book-summary">
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<nav role="navigation">
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<ul class="summary">
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<li class="chapter " data-level="0" data-path="index.html">
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<a href="../index.html">
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<i class="fa fa-check"></i>
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前言
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</a>
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<ul class="articles">
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<li class="chapter " data-level="0.1" data-path="ch0/ch0-01.html">
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<a href="../ch0/ch0-01.html">
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<i class="fa fa-check"></i>
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<b>0.1.</b>
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Go語言起源
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</a>
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</li>
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<li class="chapter " data-level="0.2" data-path="ch0/ch0-02.html">
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<a href="../ch0/ch0-02.html">
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<i class="fa fa-check"></i>
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<b>0.2.</b>
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Go語言項目
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</a>
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</li>
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<li class="chapter " data-level="0.3" data-path="ch0/ch0-03.html">
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<a href="../ch0/ch0-03.html">
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<i class="fa fa-check"></i>
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<b>0.3.</b>
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本書的組織
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</a>
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</li>
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<li class="chapter " data-level="0.4" data-path="ch0/ch0-04.html">
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<a href="../ch0/ch0-04.html">
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<i class="fa fa-check"></i>
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<b>0.4.</b>
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更多的信息
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</a>
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</li>
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<li class="chapter " data-level="0.5" data-path="ch0/ch0-05.html">
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<a href="../ch0/ch0-05.html">
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<i class="fa fa-check"></i>
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<b>0.5.</b>
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致謝
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="1" data-path="ch1/ch1.html">
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<a href="../ch1/ch1.html">
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<i class="fa fa-check"></i>
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<b>1.</b>
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入門
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</a>
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<ul class="articles">
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<li class="chapter " data-level="1.1" data-path="ch1/ch1-01.html">
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<a href="../ch1/ch1-01.html">
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<i class="fa fa-check"></i>
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<b>1.1.</b>
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Hello, World
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</a>
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</li>
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<li class="chapter " data-level="1.2" data-path="ch1/ch1-02.html">
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<a href="../ch1/ch1-02.html">
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<i class="fa fa-check"></i>
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<b>1.2.</b>
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命令行參數
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</a>
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</li>
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<li class="chapter " data-level="1.3" data-path="ch1/ch1-03.html">
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<a href="../ch1/ch1-03.html">
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<i class="fa fa-check"></i>
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<b>1.3.</b>
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査找重複的行
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</a>
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</li>
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<li class="chapter " data-level="1.4" data-path="ch1/ch1-04.html">
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<a href="../ch1/ch1-04.html">
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<i class="fa fa-check"></i>
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<b>1.4.</b>
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GIF動畵
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</a>
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</li>
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<li class="chapter " data-level="1.5" data-path="ch1/ch1-05.html">
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<a href="../ch1/ch1-05.html">
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<i class="fa fa-check"></i>
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<b>1.5.</b>
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獲取URL
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</a>
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</li>
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<li class="chapter " data-level="1.6" data-path="ch1/ch1-06.html">
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<a href="../ch1/ch1-06.html">
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<i class="fa fa-check"></i>
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<b>1.6.</b>
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併發獲取多個URL
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</a>
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</li>
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<li class="chapter " data-level="1.7" data-path="ch1/ch1-07.html">
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<a href="../ch1/ch1-07.html">
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<i class="fa fa-check"></i>
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<b>1.7.</b>
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Web服務
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</a>
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</li>
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<li class="chapter " data-level="1.8" data-path="ch1/ch1-08.html">
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<a href="../ch1/ch1-08.html">
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<i class="fa fa-check"></i>
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<b>1.8.</b>
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本章要點
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="2" data-path="ch2/ch2.html">
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<a href="../ch2/ch2.html">
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<i class="fa fa-check"></i>
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<b>2.</b>
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程序結構
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</a>
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<ul class="articles">
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<li class="chapter " data-level="2.1" data-path="ch2/ch2-01.html">
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<a href="../ch2/ch2-01.html">
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<i class="fa fa-check"></i>
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<b>2.1.</b>
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命名
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</a>
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</li>
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<li class="chapter " data-level="2.2" data-path="ch2/ch2-02.html">
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<a href="../ch2/ch2-02.html">
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<i class="fa fa-check"></i>
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<b>2.2.</b>
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聲明
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</a>
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</li>
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<li class="chapter " data-level="2.3" data-path="ch2/ch2-03.html">
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<a href="../ch2/ch2-03.html">
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<i class="fa fa-check"></i>
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<b>2.3.</b>
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變量
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</a>
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</li>
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<li class="chapter " data-level="2.4" data-path="ch2/ch2-04.html">
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<a href="../ch2/ch2-04.html">
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<i class="fa fa-check"></i>
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<b>2.4.</b>
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賦值
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</a>
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</li>
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<li class="chapter " data-level="2.5" data-path="ch2/ch2-05.html">
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<a href="../ch2/ch2-05.html">
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<i class="fa fa-check"></i>
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<b>2.5.</b>
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類型
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</a>
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</li>
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<li class="chapter " data-level="2.6" data-path="ch2/ch2-06.html">
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<a href="../ch2/ch2-06.html">
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<i class="fa fa-check"></i>
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<b>2.6.</b>
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包和文件
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</a>
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</li>
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<li class="chapter " data-level="2.7" data-path="ch2/ch2-07.html">
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<a href="../ch2/ch2-07.html">
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<i class="fa fa-check"></i>
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<b>2.7.</b>
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作用域
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="3" data-path="ch3/ch3.html">
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<a href="../ch3/ch3.html">
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<i class="fa fa-check"></i>
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<b>3.</b>
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基礎數據類型
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</a>
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<ul class="articles">
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<li class="chapter " data-level="3.1" data-path="ch3/ch3-01.html">
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<a href="../ch3/ch3-01.html">
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<i class="fa fa-check"></i>
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<b>3.1.</b>
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整型
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</a>
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</li>
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<li class="chapter " data-level="3.2" data-path="ch3/ch3-02.html">
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<a href="../ch3/ch3-02.html">
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<i class="fa fa-check"></i>
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<b>3.2.</b>
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浮點數
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</a>
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</li>
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<li class="chapter " data-level="3.3" data-path="ch3/ch3-03.html">
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<a href="../ch3/ch3-03.html">
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<i class="fa fa-check"></i>
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<b>3.3.</b>
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複數
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</a>
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</li>
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<li class="chapter " data-level="3.4" data-path="ch3/ch3-04.html">
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<a href="../ch3/ch3-04.html">
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<i class="fa fa-check"></i>
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<b>3.4.</b>
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布爾型
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</a>
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</li>
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<li class="chapter " data-level="3.5" data-path="ch3/ch3-05.html">
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<a href="../ch3/ch3-05.html">
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<i class="fa fa-check"></i>
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<b>3.5.</b>
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字符串
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</a>
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</li>
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<li class="chapter " data-level="3.6" data-path="ch3/ch3-06.html">
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<a href="../ch3/ch3-06.html">
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<i class="fa fa-check"></i>
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<b>3.6.</b>
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常量
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="4" data-path="ch4/ch4.html">
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<a href="../ch4/ch4.html">
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<i class="fa fa-check"></i>
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<b>4.</b>
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複合數據類型
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</a>
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<ul class="articles">
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<li class="chapter " data-level="4.1" data-path="ch4/ch4-01.html">
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<a href="../ch4/ch4-01.html">
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<i class="fa fa-check"></i>
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<b>4.1.</b>
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數組
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</a>
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</li>
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<li class="chapter " data-level="4.2" data-path="ch4/ch4-02.html">
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<a href="../ch4/ch4-02.html">
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<i class="fa fa-check"></i>
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<b>4.2.</b>
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Slice
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</a>
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</li>
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<li class="chapter " data-level="4.3" data-path="ch4/ch4-03.html">
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<a href="../ch4/ch4-03.html">
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<i class="fa fa-check"></i>
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<b>4.3.</b>
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Map
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</a>
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</li>
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<li class="chapter " data-level="4.4" data-path="ch4/ch4-04.html">
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<a href="../ch4/ch4-04.html">
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<i class="fa fa-check"></i>
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<b>4.4.</b>
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結構體
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</a>
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</li>
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<li class="chapter " data-level="4.5" data-path="ch4/ch4-05.html">
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<a href="../ch4/ch4-05.html">
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<i class="fa fa-check"></i>
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<b>4.5.</b>
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JSON
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</a>
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</li>
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<li class="chapter " data-level="4.6" data-path="ch4/ch4-06.html">
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<a href="../ch4/ch4-06.html">
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<i class="fa fa-check"></i>
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<b>4.6.</b>
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文本和HTML模闆
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="5" data-path="ch5/ch5.html">
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<a href="../ch5/ch5.html">
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<i class="fa fa-check"></i>
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<b>5.</b>
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函數
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</a>
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<ul class="articles">
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<li class="chapter " data-level="5.1" data-path="ch5/ch5-01.html">
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<a href="../ch5/ch5-01.html">
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<i class="fa fa-check"></i>
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<b>5.1.</b>
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函數聲明
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</a>
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</li>
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<li class="chapter " data-level="5.2" data-path="ch5/ch5-02.html">
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<a href="../ch5/ch5-02.html">
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<i class="fa fa-check"></i>
|
|
|
|
<b>5.2.</b>
|
|
|
|
遞歸
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.3" data-path="ch5/ch5-03.html">
|
|
|
|
|
|
<a href="../ch5/ch5-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.3.</b>
|
|
|
|
多返迴值
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.4" data-path="ch5/ch5-04.html">
|
|
|
|
|
|
<a href="../ch5/ch5-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.4.</b>
|
|
|
|
錯誤
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.5" data-path="ch5/ch5-05.html">
|
|
|
|
|
|
<a href="../ch5/ch5-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.5.</b>
|
|
|
|
函數值
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.6" data-path="ch5/ch5-06.html">
|
|
|
|
|
|
<a href="../ch5/ch5-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.6.</b>
|
|
|
|
匿名函數
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.7" data-path="ch5/ch5-07.html">
|
|
|
|
|
|
<a href="../ch5/ch5-07.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.7.</b>
|
|
|
|
可變參數
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.8" data-path="ch5/ch5-08.html">
|
|
|
|
|
|
<a href="../ch5/ch5-08.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.8.</b>
|
|
|
|
Deferred函數
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.9" data-path="ch5/ch5-09.html">
|
|
|
|
|
|
<a href="../ch5/ch5-09.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.9.</b>
|
|
|
|
Panic異常
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="5.10" data-path="ch5/ch5-10.html">
|
|
|
|
|
|
<a href="../ch5/ch5-10.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>5.10.</b>
|
|
|
|
Recover捕獲異常
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="6" data-path="ch6/ch6.html">
|
|
|
|
|
|
<a href="../ch6/ch6.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.</b>
|
|
|
|
方法
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="6.1" data-path="ch6/ch6-01.html">
|
|
|
|
|
|
<a href="../ch6/ch6-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.1.</b>
|
|
|
|
方法聲明
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="6.2" data-path="ch6/ch6-02.html">
|
|
|
|
|
|
<a href="../ch6/ch6-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.2.</b>
|
|
|
|
基於指針對象的方法
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="6.3" data-path="ch6/ch6-03.html">
|
|
|
|
|
|
<a href="../ch6/ch6-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.3.</b>
|
|
|
|
通過嵌入結構體來擴展類型
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="6.4" data-path="ch6/ch6-04.html">
|
|
|
|
|
|
<a href="../ch6/ch6-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.4.</b>
|
|
|
|
方法值和方法表達式
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="6.5" data-path="ch6/ch6-05.html">
|
|
|
|
|
|
<a href="../ch6/ch6-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.5.</b>
|
|
|
|
示例: Bit數組
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="6.6" data-path="ch6/ch6-06.html">
|
|
|
|
|
|
<a href="../ch6/ch6-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>6.6.</b>
|
|
|
|
封裝
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7" data-path="ch7/ch7.html">
|
|
|
|
|
|
<a href="../ch7/ch7.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.</b>
|
|
|
|
接口
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="7.1" data-path="ch7/ch7-01.html">
|
|
|
|
|
|
<a href="../ch7/ch7-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.1.</b>
|
|
|
|
接口是合約
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.2" data-path="ch7/ch7-02.html">
|
|
|
|
|
|
<a href="../ch7/ch7-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.2.</b>
|
|
|
|
接口類型
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.3" data-path="ch7/ch7-03.html">
|
|
|
|
|
|
<a href="../ch7/ch7-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.3.</b>
|
|
|
|
實現接口的條件
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.4" data-path="ch7/ch7-04.html">
|
|
|
|
|
|
<a href="../ch7/ch7-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.4.</b>
|
|
|
|
flag.Value接口
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.5" data-path="ch7/ch7-05.html">
|
|
|
|
|
|
<a href="../ch7/ch7-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.5.</b>
|
|
|
|
接口值
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.6" data-path="ch7/ch7-06.html">
|
|
|
|
|
|
<a href="../ch7/ch7-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.6.</b>
|
|
|
|
sort.Interface接口
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.7" data-path="ch7/ch7-07.html">
|
|
|
|
|
|
<a href="../ch7/ch7-07.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.7.</b>
|
|
|
|
http.Handler接口
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.8" data-path="ch7/ch7-08.html">
|
|
|
|
|
|
<a href="../ch7/ch7-08.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.8.</b>
|
|
|
|
error接口
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.9" data-path="ch7/ch7-09.html">
|
|
|
|
|
|
<a href="../ch7/ch7-09.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.9.</b>
|
|
|
|
示例: 表達式求值
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.10" data-path="ch7/ch7-10.html">
|
|
|
|
|
|
<a href="../ch7/ch7-10.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.10.</b>
|
|
|
|
類型斷言
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.11" data-path="ch7/ch7-11.html">
|
|
|
|
|
|
<a href="../ch7/ch7-11.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.11.</b>
|
|
|
|
基於類型斷言識别錯誤類型
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.12" data-path="ch7/ch7-12.html">
|
|
|
|
|
|
<a href="../ch7/ch7-12.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.12.</b>
|
|
|
|
通過類型斷言査詢接口
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.13" data-path="ch7/ch7-13.html">
|
|
|
|
|
|
<a href="../ch7/ch7-13.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.13.</b>
|
|
|
|
類型分支
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.14" data-path="ch7/ch7-14.html">
|
|
|
|
|
|
<a href="../ch7/ch7-14.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.14.</b>
|
|
|
|
示例: 基於標記的XML解碼
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="7.15" data-path="ch7/ch7-15.html">
|
|
|
|
|
|
<a href="../ch7/ch7-15.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>7.15.</b>
|
|
|
|
補充幾點
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8" data-path="ch8/ch8.html">
|
|
|
|
|
|
<a href="../ch8/ch8.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.</b>
|
|
|
|
Goroutines和Channels
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="8.1" data-path="ch8/ch8-01.html">
|
|
|
|
|
|
<a href="../ch8/ch8-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.1.</b>
|
|
|
|
Goroutines
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.2" data-path="ch8/ch8-02.html">
|
|
|
|
|
|
<a href="../ch8/ch8-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.2.</b>
|
|
|
|
示例: 併發的Clock服務
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.3" data-path="ch8/ch8-03.html">
|
|
|
|
|
|
<a href="../ch8/ch8-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.3.</b>
|
|
|
|
示例: 併發的Echo服務
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.4" data-path="ch8/ch8-04.html">
|
|
|
|
|
|
<a href="../ch8/ch8-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.4.</b>
|
|
|
|
Channels
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.5" data-path="ch8/ch8-05.html">
|
|
|
|
|
|
<a href="../ch8/ch8-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.5.</b>
|
|
|
|
併行的循環
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.6" data-path="ch8/ch8-06.html">
|
|
|
|
|
|
<a href="../ch8/ch8-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.6.</b>
|
|
|
|
示例: 併發的Web爬蟲
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.7" data-path="ch8/ch8-07.html">
|
|
|
|
|
|
<a href="../ch8/ch8-07.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.7.</b>
|
|
|
|
基於select的多路複用
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.8" data-path="ch8/ch8-08.html">
|
|
|
|
|
|
<a href="../ch8/ch8-08.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.8.</b>
|
|
|
|
示例: 併發的字典遍歷
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.9" data-path="ch8/ch8-09.html">
|
|
|
|
|
|
<a href="../ch8/ch8-09.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.9.</b>
|
|
|
|
併發的退出
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="8.10" data-path="ch8/ch8-10.html">
|
|
|
|
|
|
<a href="../ch8/ch8-10.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>8.10.</b>
|
|
|
|
示例: 聊天服務
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="9" data-path="ch9/ch9.html">
|
|
|
|
|
|
<a href="../ch9/ch9.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>9.</b>
|
|
|
|
基於共享變量的併發
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="9.1" data-path="ch9/ch9-01.html">
|
|
|
|
|
|
<a href="../ch9/ch9-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>9.1.</b>
|
|
|
|
競爭條件
|
|
</a>
|
|
|
|
|
|
</li>
|
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|
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<li class="chapter " data-level="9.2" data-path="ch9/ch9-02.html">
|
|
|
|
|
|
<a href="../ch9/ch9-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
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<b>9.2.</b>
|
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sync.Mutex互斥鎖
|
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</a>
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|
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|
|
|
</li>
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|
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<li class="chapter " data-level="9.3" data-path="ch9/ch9-03.html">
|
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|
|
|
|
<a href="../ch9/ch9-03.html">
|
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|
|
<i class="fa fa-check"></i>
|
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<b>9.3.</b>
|
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sync.RWMutex讀寫鎖
|
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</a>
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|
|
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</li>
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<li class="chapter " data-level="9.4" data-path="ch9/ch9-04.html">
|
|
|
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|
|
<a href="../ch9/ch9-04.html">
|
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<i class="fa fa-check"></i>
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<b>9.4.</b>
|
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|
|
內存同步
|
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</a>
|
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</li>
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<li class="chapter " data-level="9.5" data-path="ch9/ch9-05.html">
|
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|
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|
<a href="../ch9/ch9-05.html">
|
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<i class="fa fa-check"></i>
|
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<b>9.5.</b>
|
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|
|
sync.Once初始化
|
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</a>
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</li>
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<li class="chapter " data-level="9.6" data-path="ch9/ch9-06.html">
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|
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|
|
<a href="../ch9/ch9-06.html">
|
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<i class="fa fa-check"></i>
|
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<b>9.6.</b>
|
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|
競爭條件檢測
|
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</a>
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</li>
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<li class="chapter " data-level="9.7" data-path="ch9/ch9-07.html">
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|
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<a href="../ch9/ch9-07.html">
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<i class="fa fa-check"></i>
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<b>9.7.</b>
|
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|
示例: 併發的非阻塞緩存
|
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</a>
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</li>
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<li class="chapter " data-level="9.8" data-path="ch9/ch9-08.html">
|
|
|
|
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|
<a href="../ch9/ch9-08.html">
|
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<i class="fa fa-check"></i>
|
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<b>9.8.</b>
|
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|
Goroutines和線程
|
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</a>
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</li>
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</ul>
|
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</li>
|
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|
|
<li class="chapter " data-level="10" data-path="ch10/ch10.html">
|
|
|
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|
<a href="../ch10/ch10.html">
|
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|
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<i class="fa fa-check"></i>
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<b>10.</b>
|
|
|
|
包和工具
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
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|
|
<li class="chapter " data-level="10.1" data-path="ch10/ch10-01.html">
|
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<a href="../ch10/ch10-01.html">
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<i class="fa fa-check"></i>
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<b>10.1.</b>
|
|
|
|
簡介
|
|
</a>
|
|
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|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="10.2" data-path="ch10/ch10-02.html">
|
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|
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<a href="../ch10/ch10-02.html">
|
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<i class="fa fa-check"></i>
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<b>10.2.</b>
|
|
|
|
導入路徑
|
|
</a>
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|
|
|
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</li>
|
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<li class="chapter " data-level="10.3" data-path="ch10/ch10-03.html">
|
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|
|
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|
<a href="../ch10/ch10-03.html">
|
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<i class="fa fa-check"></i>
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<b>10.3.</b>
|
|
|
|
包聲明
|
|
</a>
|
|
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|
|
|
</li>
|
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|
|
<li class="chapter " data-level="10.4" data-path="ch10/ch10-04.html">
|
|
|
|
|
|
<a href="../ch10/ch10-04.html">
|
|
|
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<i class="fa fa-check"></i>
|
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<b>10.4.</b>
|
|
|
|
導入聲明
|
|
</a>
|
|
|
|
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|
</li>
|
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|
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<li class="chapter " data-level="10.5" data-path="ch10/ch10-05.html">
|
|
|
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|
<a href="../ch10/ch10-05.html">
|
|
|
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<i class="fa fa-check"></i>
|
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<b>10.5.</b>
|
|
|
|
匿名導入
|
|
</a>
|
|
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|
|
|
</li>
|
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<li class="chapter " data-level="10.6" data-path="ch10/ch10-06.html">
|
|
|
|
|
|
<a href="../ch10/ch10-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
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<b>10.6.</b>
|
|
|
|
包和命名
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="10.7" data-path="ch10/ch10-07.html">
|
|
|
|
|
|
<a href="../ch10/ch10-07.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>10.7.</b>
|
|
|
|
工具
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="11" data-path="ch11/ch11.html">
|
|
|
|
|
|
<a href="../ch11/ch11.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.</b>
|
|
|
|
測試
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="11.1" data-path="ch11/ch11-01.html">
|
|
|
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|
|
<a href="../ch11/ch11-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.1.</b>
|
|
|
|
go test
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="11.2" data-path="ch11/ch11-02.html">
|
|
|
|
|
|
<a href="../ch11/ch11-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.2.</b>
|
|
|
|
測試函數
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="11.3" data-path="ch11/ch11-03.html">
|
|
|
|
|
|
<a href="../ch11/ch11-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.3.</b>
|
|
|
|
測試覆蓋率
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="11.4" data-path="ch11/ch11-04.html">
|
|
|
|
|
|
<a href="../ch11/ch11-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.4.</b>
|
|
|
|
基準測試
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="11.5" data-path="ch11/ch11-05.html">
|
|
|
|
|
|
<a href="../ch11/ch11-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.5.</b>
|
|
|
|
剖析
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="11.6" data-path="ch11/ch11-06.html">
|
|
|
|
|
|
<a href="../ch11/ch11-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>11.6.</b>
|
|
|
|
示例函數
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12" data-path="ch12/ch12.html">
|
|
|
|
|
|
<a href="../ch12/ch12.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.</b>
|
|
|
|
反射
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="12.1" data-path="ch12/ch12-01.html">
|
|
|
|
|
|
<a href="../ch12/ch12-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.1.</b>
|
|
|
|
爲何需要反射?
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.2" data-path="ch12/ch12-02.html">
|
|
|
|
|
|
<a href="../ch12/ch12-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.2.</b>
|
|
|
|
reflect.Type和reflect.Value
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.3" data-path="ch12/ch12-03.html">
|
|
|
|
|
|
<a href="../ch12/ch12-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.3.</b>
|
|
|
|
Display遞歸打印
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter active" data-level="12.4" data-path="ch12/ch12-04.html">
|
|
|
|
|
|
<a href="../ch12/ch12-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.4.</b>
|
|
|
|
示例: 編碼S表達式
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.5" data-path="ch12/ch12-05.html">
|
|
|
|
|
|
<a href="../ch12/ch12-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.5.</b>
|
|
|
|
通過reflect.Value脩改值
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.6" data-path="ch12/ch12-06.html">
|
|
|
|
|
|
<a href="../ch12/ch12-06.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.6.</b>
|
|
|
|
示例: 解碼S表達式
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.7" data-path="ch12/ch12-07.html">
|
|
|
|
|
|
<a href="../ch12/ch12-07.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.7.</b>
|
|
|
|
獲取結構體字段標識
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.8" data-path="ch12/ch12-08.html">
|
|
|
|
|
|
<a href="../ch12/ch12-08.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.8.</b>
|
|
|
|
顯示一個類型的方法集
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="12.9" data-path="ch12/ch12-09.html">
|
|
|
|
|
|
<a href="../ch12/ch12-09.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>12.9.</b>
|
|
|
|
幾點忠告
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="13" data-path="ch13/ch13.html">
|
|
|
|
|
|
<a href="../ch13/ch13.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>13.</b>
|
|
|
|
底層編程
|
|
</a>
|
|
|
|
|
|
<ul class="articles">
|
|
|
|
|
|
<li class="chapter " data-level="13.1" data-path="ch13/ch13-01.html">
|
|
|
|
|
|
<a href="../ch13/ch13-01.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>13.1.</b>
|
|
|
|
unsafe.Sizeof, Alignof 和 Offsetof
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="13.2" data-path="ch13/ch13-02.html">
|
|
|
|
|
|
<a href="../ch13/ch13-02.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>13.2.</b>
|
|
|
|
unsafe.Pointer
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="13.3" data-path="ch13/ch13-03.html">
|
|
|
|
|
|
<a href="../ch13/ch13-03.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>13.3.</b>
|
|
|
|
示例: 深度相等判斷
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="13.4" data-path="ch13/ch13-04.html">
|
|
|
|
|
|
<a href="../ch13/ch13-04.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>13.4.</b>
|
|
|
|
通過cgo調用C代碼
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="13.5" data-path="ch13/ch13-05.html">
|
|
|
|
|
|
<a href="../ch13/ch13-05.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>13.5.</b>
|
|
|
|
幾點忠告
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li class="chapter " data-level="14" data-path="CONTRIBUTORS.html">
|
|
|
|
|
|
<a href="../CONTRIBUTORS.html">
|
|
|
|
<i class="fa fa-check"></i>
|
|
|
|
<b>14.</b>
|
|
|
|
附録
|
|
</a>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
|
|
|
|
<li class="divider"></li>
|
|
<li>
|
|
<a href="https://www.gitbook.com" target="blank" class="gitbook-link">
|
|
本書使用 GitBook 釋出
|
|
</a>
|
|
</li>
|
|
|
|
</ul>
|
|
</nav>
|
|
</div>
|
|
|
|
<div class="book-body">
|
|
<div class="body-inner">
|
|
<div class="book-header" role="navigation">
|
|
<!-- Actions Left -->
|
|
|
|
|
|
<!-- Title -->
|
|
<h1>
|
|
<i class="fa fa-circle-o-notch fa-spin"></i>
|
|
<a href="../" >Go语言圣经</a>
|
|
</h1>
|
|
</div>
|
|
|
|
<div class="page-wrapper" tabindex="-1" role="main">
|
|
<div class="page-inner">
|
|
|
|
|
|
<section class="normal" id="section-">
|
|
|
|
<h2 id="124-示例-編碼s表達式">12.4. 示例: 編碼S表達式</h2>
|
|
<p>Display是一個用於顯示結構化數據的調試工具，但是它併不能將任意的Go語言對象編碼爲通用消息然後用於進程間通信。</p>
|
|
<p>正如我們在4.5節中中看到的，Go語言的標準庫支持了包括JSON、XML和ASN.1等多種編碼格式。還有另一種依然被廣泛使用的格式是S表達式格式，采用類似Lisp語言的語法。但是和其他編碼格式不同的是，Go語言自帶的標準庫併不支持S表達式，主要是因爲它沒有一個公認的標準規范。</p>
|
|
<p>在本節中，我們將定義一個包用於將Go語言的對象編碼爲S表達式格式，它支持以下結構：</p>
|
|
<pre><code>42 integer
|
|
"hello" string (with Go-style quotation)
|
|
foo symbol (an unquoted name)
|
|
(1 2 3) list (zero or more items enclosed in parentheses)
|
|
</code></pre><p>布爾型習慣上使用t符號表示true，空列表或nil符號表示false，但是爲了簡單起見，我們暫時忽略布爾類型。同時忽略的還有chan管道和函數，因爲通過反射併無法知道它們的確切狀態。我們忽略的還浮點數、複數和interface。支持它們是練習12.3的任務。</p>
|
|
<p>我們將Go語言的類型編碼爲S表達式的方法如下。整數和字符串以自然的方式編碼。Nil值編碼爲nil符號。數組和slice被編碼爲一個列表。</p>
|
|
<p>結構體被編碼爲成員對象的列表，每個成員對象對應一個個僅有兩個元素的子列表，其中子列表的第一個元素是成員的名字，子列表的第二個元素是成員的值。Map被編碼爲鍵值對的列表。傳統上，S表達式使用點狀符號列表(key . value)結構來表示key/value對，而不是用一個含雙元素的列表，不過爲了簡單我們忽略了點狀符號列表。</p>
|
|
<p>編碼是由一個encode遞歸函數完成，如下所示。它的結構本質上和前面的Display函數類似：</p>
|
|
<pre><code class="lang-Go">gopl.io/ch12/sexpr
|
|
|
|
<span class="hljs-keyword">func</span> encode(buf *bytes.Buffer, v reflect.Value) error {
|
|
<span class="hljs-keyword">switch</span> v.Kind() {
|
|
<span class="hljs-keyword">case</span> reflect.Invalid:
|
|
buf.WriteString(<span class="hljs-string">"nil"</span>)
|
|
|
|
<span class="hljs-keyword">case</span> reflect.Int, reflect.Int8, reflect.Int16,
|
|
reflect.Int32, reflect.Int64:
|
|
fmt.Fprintf(buf, <span class="hljs-string">"%d"</span>, v.Int())
|
|
|
|
<span class="hljs-keyword">case</span> reflect.Uint, reflect.Uint8, reflect.Uint16,
|
|
reflect.Uint32, reflect.Uint64, reflect.Uintptr:
|
|
fmt.Fprintf(buf, <span class="hljs-string">"%d"</span>, v.Uint())
|
|
|
|
<span class="hljs-keyword">case</span> reflect.String:
|
|
fmt.Fprintf(buf, <span class="hljs-string">"%q"</span>, v.String())
|
|
|
|
<span class="hljs-keyword">case</span> reflect.Ptr:
|
|
<span class="hljs-keyword">return</span> encode(buf, v.Elem())
|
|
|
|
<span class="hljs-keyword">case</span> reflect.Array, reflect.Slice: <span class="hljs-comment">// (value ...)</span>
|
|
buf.WriteByte(<span class="hljs-string">'('</span>)
|
|
<span class="hljs-keyword">for</span> i := <span class="hljs-number">0</span>; i < v.Len(); i++ {
|
|
<span class="hljs-keyword">if</span> i > <span class="hljs-number">0</span> {
|
|
buf.WriteByte(<span class="hljs-string">' '</span>)
|
|
}
|
|
<span class="hljs-keyword">if</span> err := encode(buf, v.Index(i)); err != <span class="hljs-constant">nil</span> {
|
|
<span class="hljs-keyword">return</span> err
|
|
}
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">')'</span>)
|
|
|
|
<span class="hljs-keyword">case</span> reflect.Struct: <span class="hljs-comment">// ((name value) ...)</span>
|
|
buf.WriteByte(<span class="hljs-string">'('</span>)
|
|
<span class="hljs-keyword">for</span> i := <span class="hljs-number">0</span>; i < v.NumField(); i++ {
|
|
<span class="hljs-keyword">if</span> i > <span class="hljs-number">0</span> {
|
|
buf.WriteByte(<span class="hljs-string">' '</span>)
|
|
}
|
|
fmt.Fprintf(buf, <span class="hljs-string">"(%s "</span>, v.Type().Field(i).Name)
|
|
<span class="hljs-keyword">if</span> err := encode(buf, v.Field(i)); err != <span class="hljs-constant">nil</span> {
|
|
<span class="hljs-keyword">return</span> err
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">')'</span>)
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">')'</span>)
|
|
|
|
<span class="hljs-keyword">case</span> reflect.Map: <span class="hljs-comment">// ((key value) ...)</span>
|
|
buf.WriteByte(<span class="hljs-string">'('</span>)
|
|
<span class="hljs-keyword">for</span> i, key := <span class="hljs-keyword">range</span> v.MapKeys() {
|
|
<span class="hljs-keyword">if</span> i > <span class="hljs-number">0</span> {
|
|
buf.WriteByte(<span class="hljs-string">' '</span>)
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">'('</span>)
|
|
<span class="hljs-keyword">if</span> err := encode(buf, key); err != <span class="hljs-constant">nil</span> {
|
|
<span class="hljs-keyword">return</span> err
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">' '</span>)
|
|
<span class="hljs-keyword">if</span> err := encode(buf, v.MapIndex(key)); err != <span class="hljs-constant">nil</span> {
|
|
<span class="hljs-keyword">return</span> err
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">')'</span>)
|
|
}
|
|
buf.WriteByte(<span class="hljs-string">')'</span>)
|
|
|
|
<span class="hljs-keyword">default</span>: <span class="hljs-comment">// float, complex, bool, chan, func, interface</span>
|
|
<span class="hljs-keyword">return</span> fmt.Errorf(<span class="hljs-string">"unsupported type: %s"</span>, v.Type())
|
|
}
|
|
<span class="hljs-keyword">return</span> <span class="hljs-constant">nil</span>
|
|
}
|
|
</code></pre>
|
|
<p>Marshal函數是對encode的保證，以保持和encoding/...下其它包有着相似的API：</p>
|
|
<pre><code class="lang-Go"><span class="hljs-comment">// Marshal encodes a Go value in S-expression form.</span>
|
|
<span class="hljs-keyword">func</span> Marshal(v <span class="hljs-keyword">interface</span>{}) ([]<span class="hljs-typename">byte</span>, error) {
|
|
<span class="hljs-keyword">var</span> buf bytes.Buffer
|
|
<span class="hljs-keyword">if</span> err := encode(&buf, reflect.ValueOf(v)); err != <span class="hljs-constant">nil</span> {
|
|
<span class="hljs-keyword">return</span> <span class="hljs-constant">nil</span>, err
|
|
}
|
|
<span class="hljs-keyword">return</span> buf.Bytes(), <span class="hljs-constant">nil</span>
|
|
}
|
|
</code></pre>
|
|
<p>下面是Marshal對12.3節的strangelove變量編碼後的結果：</p>
|
|
<pre><code>((Title "Dr. Strangelove") (Subtitle "How I Learned to Stop Worrying and Lo
|
|
ve the Bomb") (Year 1964) (Actor (("Grp. Capt. Lionel Mandrake" "Peter Sell
|
|
ers") ("Pres. Merkin Muffley" "Peter Sellers") ("Gen. Buck Turgidson" "Geor
|
|
ge C. Scott") ("Brig. Gen. Jack D. Ripper" "Sterling Hayden") ("Maj. T.J. \
|
|
"King\" Kong" "Slim Pickens") ("Dr. Strangelove" "Peter Sellers"))) (Oscars
|
|
("Best Actor (Nomin.)" "Best Adapted Screenplay (Nomin.)" "Best Director (N
|
|
omin.)" "Best Picture (Nomin.)")) (Sequel nil))
|
|
</code></pre><p>整個輸出編碼爲一行中以減少輸出的大小，但是也很難閲讀。這里有一個對S表達式格式化的約定。編寫一個S表達式的格式化函數將作爲一個具有挑戰性的練習任務；不過 <a href="http://gopl.io" target="_blank">http://gopl.io</a> 也提供了一個簡單的版本。</p>
|
|
<pre><code>((Title "Dr. Strangelove")
|
|
(Subtitle "How I Learned to Stop Worrying and Love the Bomb")
|
|
(Year 1964)
|
|
(Actor (("Grp. Capt. Lionel Mandrake" "Peter Sellers")
|
|
("Pres. Merkin Muffley" "Peter Sellers")
|
|
("Gen. Buck Turgidson" "George C. Scott")
|
|
("Brig. Gen. Jack D. Ripper" "Sterling Hayden")
|
|
("Maj. T.J. \"King\" Kong" "Slim Pickens")
|
|
("Dr. Strangelove" "Peter Sellers")))
|
|
(Oscars ("Best Actor (Nomin.)"
|
|
"Best Adapted Screenplay (Nomin.)"
|
|
"Best Director (Nomin.)"
|
|
"Best Picture (Nomin.)"))
|
|
(Sequel nil))
|
|
</code></pre><p>和fmt.Print、json.Marshal、Display函數類似，sexpr.Marshal函數處理帶環的數據結構也會陷入死循環。</p>
|
|
<p>在12.6節中，我們將給出S表達式解碼器的實現步驟，但是在那之前，我們還需要先了解如果通過反射技術來更新程序的變量。</p>
|
|
<p><strong>練習 12.3：</strong> 實現encode函數缺少的分支。將布爾類型編碼爲t和nil，浮點數編碼爲Go語言的格式，複數1+2i編碼爲#C(1.0 2.0)格式。接口編碼爲類型名和值對，例如("[]int" (1 2 3))，但是這個形式可能會造成歧義：reflect.Type.String方法對於不同的類型可能返迴相同的結果。</p>
|
|
<p><strong>練習 12.4：</strong> 脩改encode函數，以上面的格式化形式輸出S表達式。</p>
|
|
<p><strong>練習 12.5：</strong> 脩改encode函數，用JSON格式代替S表達式格式。然後使用標準庫提供的json.Unmarshal解碼器來驗證函數是正確的。</p>
|
|
<p><strong>練習 12.6：</strong> 脩改encode，作爲一個優化，忽略對是零值對象的編碼。</p>
|
|
<p><strong>練習 12.7：</strong> 創建一個基於流式的API，用於S表達式的解碼，和json.Decoder(§4.5)函數功能類似。</p>
|
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</section>
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