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add unassigned slice example (#475)

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jiangbo 2023-05-17 02:04:20 +08:00 committed by GitHub
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4 changed files with 35 additions and 13 deletions
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9
examples/slices/slices.go
View File

@ -9,11 +9,16 @@ func main() {
// Unlike arrays, slices are typed only by the
// elements they contain (not the number of elements).
// unassigned slice equal to nil and has a length of `0`
var s []string
fmt.Println("unassigned:", s, s == nil, len(s) == 0)
// To create an empty slice with non-zero length, use
// the builtin `make`. Here we make a slice of
// `string`s of length `3` (initially zero-valued).
s := make([]string, 3)
fmt.Println("emp:", s)
// `string`s of capacity `5`.
s = make([]string, 3, 5)
fmt.Println("emp:", s, "len:", len(s), "cap:", cap(s))
// We can set and get just like with arrays.
s[0] = "a"

4
examples/slices/slices.hash
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@ -1,2 +1,2 @@
13835b88336e031808f2f3887cd43d0b9d85cad0
76f4Jif5Z8o
d255a550fe04d6a6d31c7256a1d980e675db0619
ryiklDqjbId

3
examples/slices/slices.sh
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@ -1,7 +1,8 @@
# Note that while slices are different types than arrays,
# they are rendered similarly by `fmt.Println`.
$ go run slices.go
emp: [ ]
unassigned: [] true true
emp: [ ] len: 3 cap: 5
set: [a b c]
get: c
len: 3

32
public/slices generated
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@ -42,7 +42,7 @@ a more powerful interface to sequences than arrays.</p>
</td>
<td class="code leading">
<a href="https://go.dev/play/p/76f4Jif5Z8o"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<a href="https://go.dev/play/p/ryiklDqjbId"><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>
@ -74,16 +74,31 @@ a more powerful interface to sequences than arrays.</p>
<td class="docs">
<p>Unlike arrays, slices are typed only by the
elements they contain (not the number of elements).
To create an empty slice with non-zero length, use
the builtin <code>make</code>. Here we make a slice of
<code>string</code>s of length <code>3</code> (initially zero-valued).</p>
unassigned slice equal to nil and has a length of <code>0</code></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">&#34;emp:&#34;</span><span class="p">,</span> <span class="nx">s</span><span class="p">)</span>
<span class="kd">var</span> <span class="nx">s</span> <span class="p">[]</span><span class="kt">string</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">&#34;unassigned:&#34;</span><span class="p">,</span> <span class="nx">s</span><span class="p">,</span> <span class="nx">s</span> <span class="o">==</span> <span class="kc">nil</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="o">==</span> <span class="mi">0</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>To create an empty slice with non-zero length, use
the builtin <code>make</code>. Here we make a slice of
<code>string</code>s of length <code>3</code> (initially zero-valued).
<code>string</code>s of capacity <code>5</code>.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">s</span> <span class="p">=</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="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">&#34;emp:&#34;</span><span class="p">,</span> <span class="nx">s</span><span class="p">,</span> <span class="s">&#34;len:&#34;</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="s">&#34;cap:&#34;</span><span class="p">,</span> <span class="nb">cap</span><span class="p">(</span><span class="nx">s</span><span class="p">))</span>
</pre>
</td>
</tr>
@ -252,7 +267,8 @@ they are rendered similarly by <code>fmt.Println</code>.</p>
<pre class="chroma">
<span class="gp">$</span> go run slices.go
<span class="go">emp: [ ]
<span class="go">unassigned: [] true true
</span><span class="go">emp: [ ] len: 3 cap: 5
</span><span class="go">set: [a b c]
</span><span class="go">get: c
</span><span class="go">len: 3
@ -306,7 +322,7 @@ Go&rsquo;s other key builtin data structure: maps.</p>
</div>
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func main() {\u000A');codeLines.push(' var s []string\u000A fmt.Println(\"unassigned:\", s, s \u003D\u003D nil, len(s) \u003D\u003D 0)\u000A');codeLines.push(' s \u003D make([]string, 3, 5)\u000A fmt.Println(\"emp:\", s, \"len:\", len(s), \"cap:\", cap(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>
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