150 lines
6.1 KiB
Plaintext
Generated
150 lines
6.1 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Channel Directions</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'channel-synchronization';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'select';
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}
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}
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</script>
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<body>
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<div class="example" id="channel-directions">
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<h2><a href="./">Go by Example</a>: Channel Directions</h2>
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<table>
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<tr>
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<td class="docs">
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<p>When using channels as function parameters, you can
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specify if a channel is meant to only send or receive
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values. This specificity increases the type-safety of
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the program.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/mjNJDHwUH4R"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><span class="kn">import</span> <span class="s">"fmt"</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>This <code>ping</code> function only accepts a channel for sending
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values. It would be a compile-time error to try to
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receive on this channel.</p>
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</td>
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<td class="code leading">
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<pre class="chroma">
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<span class="kd">func</span> <span class="nf">ping</span><span class="p">(</span><span class="nx">pings</span> <span class="kd">chan</span><span class="o"><-</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">msg</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">pings</span> <span class="o"><-</span> <span class="nx">msg</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>The <code>pong</code> function accepts one channel for receives
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(<code>pings</code>) and a second for sends (<code>pongs</code>).</p>
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</td>
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<td class="code leading">
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<pre class="chroma">
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<span class="kd">func</span> <span class="nf">pong</span><span class="p">(</span><span class="nx">pings</span> <span class="o"><-</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">pongs</span> <span class="kd">chan</span><span class="o"><-</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">msg</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">pings</span>
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<span class="nx">pongs</span> <span class="o"><-</span> <span class="nx">msg</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
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<span class="nx">pings</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
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<span class="nx">pongs</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
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<span class="nf">ping</span><span class="p">(</span><span class="nx">pings</span><span class="p">,</span> <span class="s">"passed message"</span><span class="p">)</span>
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<span class="nf">pong</span><span class="p">(</span><span class="nx">pings</span><span class="p">,</span> <span class="nx">pongs</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="o"><-</span><span class="nx">pongs</span><span class="p">)</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<pre class="chroma"><span class="gp">$</span> go run channel-directions.go
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<span class="go">passed message</span></pre>
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="select">Select</a>.
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</p>
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<p class="footer">
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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>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func ping(pings chan\u003C- string, msg string) {\u000A pings \u003C- msg\u000A}\u000A');codeLines.push('func pong(pings \u003C-chan string, pongs chan\u003C- string) {\u000A msg :\u003D \u003C-pings\u000A pongs \u003C- msg\u000A}\u000A');codeLines.push('func main() {\u000A pings :\u003D make(chan string, 1)\u000A pongs :\u003D make(chan string, 1)\u000A ping(pings, \"passed message\")\u000A pong(pings, pongs)\u000A fmt.Println(\u003C-pongs)\u000A}\u000A');codeLines.push('');
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</script>
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</body>
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</html>
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