forked from gobyexample-cn/gobyexample-cn.github.io
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathslices.html
299 lines (232 loc) · 15.3 KB
/
slices.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
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 切片</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'arrays';
}
if (e.key == "ArrowRight") {
window.location.href = 'maps';
}
}
</script>
<body>
<div class="example" id="slices">
<h2><a href="./">Go by Example 中文版</a>: 切片</h2>
<table>
<tr>
<td class="docs">
<p><em>Slice</em> 是 Go 中一个重要的数据类型，它提供了比数组更强大的序列交互方式。</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/qC32TQNNUoC"><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>与数组不同，slice 的类型仅由它所包含的元素的类型决定（与元素个数无关）。
要创建一个长度不为 0 的空 slice，需要使用内建函数 <code>make</code>。
这里我们创建了一个长度为 3 的 <code>string</code> 类型的 slice（初始值为零值）。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">s</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">string</span><span class="p">,</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">"emp:"</span><span class="p">,</span> <span class="nx">s</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>我们可以和数组一样设置和得到值</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">s</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="p">=</span> <span class="s">"a"</span>
<span class="nx">s</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="p">=</span> <span class="s">"b"</span>
<span class="nx">s</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="p">=</span> <span class="s">"c"</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"set:"</span><span class="p">,</span> <span class="nx">s</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">"get:"</span><span class="p">,</span> <span class="nx">s</span><span class="p">[</span><span class="mi">2</span><span class="p">])</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>len</code> 返回 slice 的长度</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"len:"</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="nx">s</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>除了基本操作外，slice 支持比数组更丰富的操作。比如 slice 支持内建函数 <code>append</code>，
该函数会返回一个包含了一个或者多个新值的 slice。
注意由于 <code>append</code> 可能返回一个新的 slice，我们需要接收其返回值。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">s</span> <span class="p">=</span> <span class="nb">append</span><span class="p">(</span><span class="nx">s</span><span class="p">,</span> <span class="s">"d"</span><span class="p">)</span>
<span class="nx">s</span> <span class="p">=</span> <span class="nb">append</span><span class="p">(</span><span class="nx">s</span><span class="p">,</span> <span class="s">"e"</span><span class="p">,</span> <span class="s">"f"</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">"apd:"</span><span class="p">,</span> <span class="nx">s</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>slice 还可以 <code>copy</code>。这里我们创建一个空的和 <code>s</code> 有相同长度的 slice——<code>c</code>，
然后将 <code>s</code> 复制给 <code>c</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">c</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">string</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="nx">s</span><span class="p">))</span>
<span class="nb">copy</span><span class="p">(</span><span class="nx">c</span><span class="p">,</span> <span class="nx">s</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">"cpy:"</span><span class="p">,</span> <span class="nx">c</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>slice 支持通过 <code>slice[low:high]</code> 语法进行“切片”操作。
例如，右边的操作可以得到一个包含元素 <code>s[2]</code>、<code>s[3]</code> 和 <code>s[4]</code> 的 slice。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">l</span> <span class="o">:=</span> <span class="nx">s</span><span class="p">[</span><span class="mi">2</span><span class="p">:</span><span class="mi">5</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">"sl1:"</span><span class="p">,</span> <span class="nx">l</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这个 slice 包含从 <code>s[0]</code> 到 <code>s[5]</code>（不包含 5）的元素。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">l</span> <span class="p">=</span> <span class="nx">s</span><span class="p">[:</span><span class="mi">5</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">"sl2:"</span><span class="p">,</span> <span class="nx">l</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这个 slice 包含从 <code>s[2]</code>（包含 2）之后的元素。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">l</span> <span class="p">=</span> <span class="nx">s</span><span class="p">[</span><span class="mi">2</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">"sl3:"</span><span class="p">,</span> <span class="nx">l</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>我们可以在一行代码中声明并初始化一个 slice 变量。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">t</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"g"</span><span class="p">,</span> <span class="s">"h"</span><span class="p">,</span> <span class="s">"i"</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">"dcl:"</span><span class="p">,</span> <span class="nx">t</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Slice 可以组成多维数据结构。内部的 slice 长度可以不一致，这一点和多维数组不同。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">twoD</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([][]</span><span class="kt">int</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
<span class="k">for</span> <span class="nx">i</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">i</span> <span class="p"><</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">i</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">innerLen</span> <span class="o">:=</span> <span class="nx">i</span> <span class="o">+</span> <span class="mi">1</span>
<span class="nx">twoD</span><span class="p">[</span><span class="nx">i</span><span class="p">]</span> <span class="p">=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">int</span><span class="p">,</span> <span class="nx">innerLen</span><span class="p">)</span>
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">j</span> <span class="p"><</span> <span class="nx">innerLen</span><span class="p">;</span> <span class="nx">j</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">twoD</span><span class="p">[</span><span class="nx">i</span><span class="p">][</span><span class="nx">j</span><span class="p">]</span> <span class="p">=</span> <span class="nx">i</span> <span class="o">+</span> <span class="nx">j</span>
<span class="p">}</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">"2d: "</span><span class="p">,</span> <span class="nx">twoD</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>注意，slice 和数组是不同的类型，但它们通过 <code>fmt.Println</code> 打印的输出结果是类似的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="gp">$</span> go run slices.go
<span class="go">emp: [ ]
</span><span class="go">set: [a b c]
</span><span class="go">get: c
</span><span class="go">len: 3
</span><span class="go">apd: [a b c d e f]
</span><span class="go">cpy: [a b c d e f]
</span><span class="go">sl1: [c d e]
</span><span class="go">sl2: [a b c d e]
</span><span class="go">sl3: [c d e f]
</span><span class="go">dcl: [g h i]
</span><span class="go">2d: [[0] [1 2] [2 3 4]]</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>看看这个由 Go 团队撰写的一篇<a href="http://blog.golang.org/2011/01/go-slices-usage-and-internals.html">很棒的博文</a>，了解更多关于 Go 中 slice 的设计和实现细节。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
<p>现在，我们已经学习了数组和 slice，接下来我们将学习 Go 中的另一个重要的内建数据类型：map。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="maps.html">Map</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(' s :\u003D make([]string, 3)\u000A fmt.Println(\"emp:\", s)\u000A');codeLines.push(' s[0] \u003D \"a\"\u000A s[1] \u003D \"b\"\u000A s[2] \u003D \"c\"\u000A fmt.Println(\"set:\", s)\u000A fmt.Println(\"get:\", s[2])\u000A');codeLines.push(' fmt.Println(\"len:\", len(s))\u000A');codeLines.push(' s \u003D append(s, \"d\")\u000A s \u003D append(s, \"e\", \"f\")\u000A fmt.Println(\"apd:\", s)\u000A');codeLines.push(' c :\u003D make([]string, len(s))\u000A copy(c, s)\u000A fmt.Println(\"cpy:\", c)\u000A');codeLines.push(' l :\u003D s[2:5]\u000A fmt.Println(\"sl1:\", l)\u000A');codeLines.push(' l \u003D s[:5]\u000A fmt.Println(\"sl2:\", l)\u000A');codeLines.push(' l \u003D s[2:]\u000A fmt.Println(\"sl3:\", l)\u000A');codeLines.push(' t :\u003D []string{\"g\", \"h\", \"i\"}\u000A fmt.Println(\"dcl:\", t)\u000A');codeLines.push(' twoD :\u003D make([][]int, 3)\u000A for i :\u003D 0; i \u003C 3; i++ {\u000A innerLen :\u003D i + 1\u000A twoD[i] \u003D make([]int, innerLen)\u000A for j :\u003D 0; j \u003C innerLen; j++ {\u000A twoD[i][j] \u003D i + j\u000A }\u000A }\u000A fmt.Println(\"2d: \", twoD)\u000A}\u000A');codeLines.push('');codeLines.push('');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>