191 lines
11 KiB
Plaintext
Generated
191 lines
11 KiB
Plaintext
Generated
<!DOCTYPE html>
|
|
<html>
|
|
<head>
|
|
<meta charset="utf-8">
|
|
<title>Go by Example: Sorting by Functions</title>
|
|
<link rel=stylesheet href="site.css">
|
|
</head>
|
|
<script>
|
|
onkeydown = (e) => {
|
|
|
|
if (e.key == "ArrowLeft") {
|
|
window.location.href = 'sorting';
|
|
}
|
|
|
|
|
|
if (e.key == "ArrowRight") {
|
|
window.location.href = 'panic';
|
|
}
|
|
|
|
}
|
|
</script>
|
|
<body>
|
|
<div class="example" id="sorting-by-functions">
|
|
<h2><a href="./">Go by Example</a>: Sorting by Functions</h2>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Sometimes we’ll want to sort a collection by something
|
|
other than its natural order. For example, suppose we
|
|
wanted to sort strings by their length instead of
|
|
alphabetically. Here’s an example of custom sorts
|
|
in Go.</p>
|
|
|
|
</td>
|
|
<td class="code empty leading">
|
|
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
<a href="https://go.dev/play/p/3EaTknAZHMu"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
|
|
<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="s">"cmp"</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="s">"slices"</span>
|
|
</span></span><span class="line"><span class="cl"><span class="p">)</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">fruits</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"peach"</span><span class="p">,</span> <span class="s">"banana"</span><span class="p">,</span> <span class="s">"kiwi"</span><span class="p">}</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>We implement a comparison function for string
|
|
lengths. <code>cmp.Compare</code> is helpful for this.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">lenCmp</span> <span class="o">:=</span> <span class="kd">func</span><span class="p">(</span><span class="nx">a</span><span class="p">,</span> <span class="nx">b</span> <span class="kt">string</span><span class="p">)</span> <span class="kt">int</span> <span class="p">{</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="nx">cmp</span><span class="p">.</span><span class="nf">Compare</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="nx">a</span><span class="p">),</span> <span class="nb">len</span><span class="p">(</span><span class="nx">b</span><span class="p">))</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="p">}</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Now we can call <code>slices.SortFunc</code> with this custom
|
|
comparison function to sort <code>fruits</code> by name length.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">slices</span><span class="p">.</span><span class="nf">SortFunc</span><span class="p">(</span><span class="nx">fruits</span><span class="p">,</span> <span class="nx">lenCmp</span><span class="p">)</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">fruits</span><span class="p">)</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>We can use the same technique to sort a slice of
|
|
values that aren’t built-in types.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="kd">type</span> <span class="nx">Person</span> <span class="kd">struct</span> <span class="p">{</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">name</span> <span class="kt">string</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">age</span> <span class="kt">int</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="p">}</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">people</span> <span class="o">:=</span> <span class="p">[]</span><span class="nx">Person</span><span class="p">{</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">Person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">"Jax"</span><span class="p">,</span> <span class="nx">age</span><span class="p">:</span> <span class="mi">37</span><span class="p">},</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">Person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">"TJ"</span><span class="p">,</span> <span class="nx">age</span><span class="p">:</span> <span class="mi">25</span><span class="p">},</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">Person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">"Alex"</span><span class="p">,</span> <span class="nx">age</span><span class="p">:</span> <span class="mi">72</span><span class="p">},</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="p">}</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Sort <code>people</code> by age using <code>slices.SortFunc</code>.</p>
|
|
|
|
<p>Note: if the <code>Person</code> struct is large,
|
|
you may want the slice to contain <code>*Person</code> instead
|
|
and adjust the sorting function accordingly. If in
|
|
doubt, <a href="testing-and-benchmarking">benchmark</a>!</p>
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">slices</span><span class="p">.</span><span class="nf">SortFunc</span><span class="p">(</span><span class="nx">people</span><span class="p">,</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="kd">func</span><span class="p">(</span><span class="nx">a</span><span class="p">,</span> <span class="nx">b</span> <span class="nx">Person</span><span class="p">)</span> <span class="kt">int</span> <span class="p">{</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="nx">cmp</span><span class="p">.</span><span class="nf">Compare</span><span class="p">(</span><span class="nx">a</span><span class="p">.</span><span class="nx">age</span><span class="p">,</span> <span class="nx">b</span><span class="p">.</span><span class="nx">age</span><span class="p">)</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="p">})</span>
|
|
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">people</span><span class="p">)</span>
|
|
</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<pre class="chroma"><code><span class="line"><span class="cl"><span class="gp">$</span> go run sorting-by-functions.go
|
|
</span></span><span class="line"><span class="cl"><span class="go">[kiwi peach banana]
|
|
</span></span></span><span class="line"><span class="cl"><span class="go">[{TJ 25} {Jax 37} {Alex 72}]</span></span></span></code></pre>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
|
|
<p class="next">
|
|
Next example: <a href="panic">Panic</a>.
|
|
</p>
|
|
|
|
|
|
<p class="footer">
|
|
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
|
|
</p>
|
|
|
|
</div>
|
|
<script>
|
|
var codeLines = [];
|
|
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"cmp\"\u000A \"fmt\"\u000A \"slices\"\u000A)\u000A');codeLines.push('func main() {\u000A fruits :\u003D []string{\"peach\", \"banana\", \"kiwi\"}\u000A');codeLines.push(' lenCmp :\u003D func(a, b string) int {\u000A return cmp.Compare(len(a), len(b))\u000A }\u000A');codeLines.push(' slices.SortFunc(fruits, lenCmp)\u000A fmt.Println(fruits)\u000A');codeLines.push(' type Person struct {\u000A name string\u000A age int\u000A }\u000A');codeLines.push(' people :\u003D []Person{\u000A Person{name: \"Jax\", age: 37},\u000A Person{name: \"TJ\", age: 25},\u000A Person{name: \"Alex\", age: 72},\u000A }\u000A');codeLines.push(' slices.SortFunc(people,\u000A func(a, b Person) int {\u000A return cmp.Compare(a.age, b.age)\u000A })\u000A fmt.Println(people)\u000A}\u000A');codeLines.push('');
|
|
</script>
|
|
<script src="site.js" async></script>
|
|
</body>
|
|
</html>
|