-
Notifications
You must be signed in to change notification settings - Fork 8
/
range.html
201 lines (157 loc) · 9.01 KB
/
range.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: Range 遍历</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'maps';
}
if (e.key == "ArrowRight") {
window.location.href = 'functions';
}
}
</script>
<body>
<div class="example" id="range">
<h2><a href="./">Go by Example 中文版</a>: Range 遍历</h2>
<table>
<tr>
<td class="docs">
<p><em>range</em> 用于迭代各种各样的数据结构。
让我们来看看如何在我们已经学过的数据结构上使用 <code>range</code>。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/-xCa-Z-M87k"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="s">"fmt"</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这里我们使用 <code>range</code> 来对 slice 中的元素求和。
数组也可以用这种方法初始化并赋初值。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">nums</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">int</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">}</span>
<span class="nx">sum</span> <span class="o">:=</span> <span class="mi">0</span>
<span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">num</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">nums</span> <span class="p">{</span>
<span class="nx">sum</span> <span class="o">+=</span> <span class="nx">num</span>
<span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"sum:"</span><span class="p">,</span> <span class="nx">sum</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>range</code> 在数组和 slice 中提供对每项的索引和值的访问。
上面我们不需要索引，所以我们使用 <em>空白标识符</em> <code>_</code> 将其忽略。
实际上，我们有时候是需要这个索引的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">i</span><span class="p">,</span> <span class="nx">num</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">nums</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">num</span> <span class="o">==</span> <span class="mi">3</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"index:"</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>range</code> 在 map 中迭代键值对。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">kvs</span> <span class="o">:=</span> <span class="kd">map</span><span class="p">[</span><span class="kt">string</span><span class="p">]</span><span class="kt">string</span><span class="p">{</span><span class="s">"a"</span><span class="p">:</span> <span class="s">"apple"</span><span class="p">,</span> <span class="s">"b"</span><span class="p">:</span> <span class="s">"banana"</span><span class="p">}</span>
<span class="k">for</span> <span class="nx">k</span><span class="p">,</span> <span class="nx">v</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">kvs</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"%s -> %s\n"</span><span class="p">,</span> <span class="nx">k</span><span class="p">,</span> <span class="nx">v</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>range</code> 也可以只遍历 map 的键。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">k</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">kvs</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"key:"</span><span class="p">,</span> <span class="nx">k</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>range</code> 在字符串中迭代 unicode 码点(code point)。
第一个返回值是字符的起始字节位置，然后第二个是字符本身。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="k">for</span> <span class="nx">i</span><span class="p">,</span> <span class="nx">c</span> <span class="o">:=</span> <span class="k">range</span> <span class="s">"go"</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">i</span><span class="p">,</span> <span class="nx">c</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"><span class="gp">$</span> go run range.go
<span class="go">sum: 9
</span><span class="go">index: 1
</span><span class="go">a -> apple
</span><span class="go">b -> banana
</span><span class="go">key: a
</span><span class="go">key: b
</span><span class="go">0 103
</span><span class="go">1 111</span></pre>
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="functions">函数</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
<script>
var codeLines = [];
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func main() {\u000A');codeLines.push(' nums :\u003D []int{2, 3, 4}\u000A sum :\u003D 0\u000A for _, num :\u003D range nums {\u000A sum +\u003D num\u000A }\u000A fmt.Println(\"sum:\", sum)\u000A');codeLines.push(' for i, num :\u003D range nums {\u000A if num \u003D\u003D 3 {\u000A fmt.Println(\"index:\", i)\u000A }\u000A }\u000A');codeLines.push(' kvs :\u003D map[string]string{\"a\": \"apple\", \"b\": \"banana\"}\u000A for k, v :\u003D range kvs {\u000A fmt.Printf(\"%s -\u003E %s\\n\", k, v)\u000A }\u000A');codeLines.push(' for k :\u003D range kvs {\u000A fmt.Println(\"key:\", k)\u000A }\u000A');codeLines.push(' for i, c :\u003D range \"go\" {\u000A fmt.Println(i, c)\u000A }\u000A}\u000A');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>