403 lines
22 KiB
Plaintext
Generated
403 lines
22 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: Text Templates</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 = 'regular-expressions';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'json';
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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="text-templates">
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<h2><a href="./">Go by Example</a>: Text Templates</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Go offers built-in support for creating
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dynamic content or showing customized output to the user called Template.</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/-mRr-NuSB6f"><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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<p>Go has two template packages. one is “text/template” for
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regular text manipulation, and another one is “html/template”
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which has the same API as “text/template” but has additional security features.
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It should be used when generating HTML.</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="kn">import</span> <span class="p">(</span>
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<span class="s">"log"</span>
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<span class="s">"os"</span>
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<span class="s">"text/template"</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 leading">
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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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</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>New creates a template with a specific name and returns a pointer to it.</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="nx">t1</span> <span class="o">:=</span> <span class="nx">template</span><span class="p">.</span><span class="nf">New</span><span class="p">(</span><span class="s">"t1"</span><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>Parse parses its parameter as template body.
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We use {{.}} to access the value passed to the template when it’s getting executed.</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="nx">t1</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">t1</span><span class="p">.</span><span class="nf">Parse</span><span class="p">(</span><span class="s">"Value is {{.}}\n"</span><span class="p">)</span>
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<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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<span class="nx">log</span><span class="p">.</span><span class="nf">Fatal</span><span class="p">(</span><span class="nx">err</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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<tr>
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<td class="docs">
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<p>If we want to ignore the errors we can use Must function.
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It will panic if an error occurs when parsing the template.</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="nx">t1</span> <span class="p">=</span> <span class="nx">template</span><span class="p">.</span><span class="nf">Must</span><span class="p">(</span><span class="nx">t1</span><span class="p">.</span><span class="nf">Parse</span><span class="p">(</span><span class="s">"Value is {{.}}\n"</span><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>Execute applies parsed template to the data we pass to it and writes the output to the io.Writer.</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="nx">t1</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="nx">t1</span><span class="p">.</span><span class="nf">Name</span><span class="p">())</span>
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<span class="nx">t1</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="s">"some text"</span><span class="p">)</span>
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<span class="nx">t1</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="kc">true</span><span class="p">)</span>
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<span class="nx">t1</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="mi">5</span><span class="p">)</span>
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<span class="nx">t1</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span>
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<span class="s">"Go"</span><span class="p">,</span>
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<span class="s">"Rust"</span><span class="p">,</span>
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<span class="s">"C++"</span><span class="p">,</span>
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<span class="s">"C#"</span><span class="p">,</span>
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<span class="p">})</span>
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<span class="nx">t1</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="kd">struct</span><span class="p">{</span> <span class="nx">name</span> <span class="kt">string</span> <span class="p">}{</span>
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<span class="nx">name</span><span class="p">:</span> <span class="s">"Jane Doe"</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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<tr>
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<td class="docs">
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<p>If the data is a struct we can use the {{.FieldName}} action to access its fields.
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The fields should be exported to be accessible when template is executing.</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="nx">t2</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">template</span><span class="p">.</span>
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<span class="nf">New</span><span class="p">(</span><span class="s">"t2"</span><span class="p">).</span>
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<span class="nf">Parse</span><span class="p">(</span><span class="s">"Fullname: {{.Fullname}}\n"</span><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 leading">
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<pre class="chroma"> <span class="nx">t2</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="kd">struct</span> <span class="p">{</span>
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<span class="nx">Fullname</span> <span class="kt">string</span>
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<span class="p">}{</span>
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<span class="nx">Fullname</span><span class="p">:</span> <span class="s">"Jane Doe"</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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<tr>
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<td class="docs">
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<p>The same applies to maps; with maps there is no restriction on the case of key names.</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="nx">t2</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</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>
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<span class="s">"Fullname"</span><span class="p">:</span> <span class="s">"Mickey Mouse"</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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<tr>
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<td class="docs">
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<p>You can use if control structure to show data conditionally.
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The data between if block will be shown if the field is truthy.
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Means it is not false boolean, empty string, nil or zero length slice, nil map/pointer.</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="nx">t3</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">template</span><span class="p">.</span>
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<span class="nf">New</span><span class="p">(</span><span class="s">"t3"</span><span class="p">).</span>
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<span class="nf">Parse</span><span class="p">(</span><span class="s">`</span><span class="cp">{{</span><span class="k">if</span><span class="w"> </span><span class="na">.Field1</span><span class="cp">}}</span><span class="s">
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</span><span class="s"> If block => </span><span class="cp">{{</span><span class="na">.Field1</span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="na">.Field2</span><span class="cp">}}</span><span class="s">
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</span><span class="s"> Else if block => </span><span class="cp">{{</span><span class="na">.Field2</span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="cp">}}</span><span class="s">
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</span><span class="s"> Else block
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="cp">}}</span><span class="s">`</span><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 leading">
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<pre class="chroma"> <span class="nx">s</span> <span class="o">:=</span> <span class="kd">struct</span> <span class="p">{</span>
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<span class="nx">Field1</span> <span class="kt">string</span>
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<span class="nx">Field2</span> <span class="p">[]</span><span class="kt">string</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 leading">
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<pre class="chroma"> <span class="nx">s</span><span class="p">.</span><span class="nx">Field1</span> <span class="p">=</span> <span class="s">""</span>
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<span class="nx">s</span><span class="p">.</span><span class="nx">Field2</span> <span class="p">=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{}</span>
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<span class="nx">t3</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="nx">s</span><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 leading">
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<pre class="chroma"> <span class="nx">s</span><span class="p">.</span><span class="nx">Field1</span> <span class="p">=</span> <span class="s">"Some text"</span>
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<span class="nx">s</span><span class="p">.</span><span class="nx">Field2</span> <span class="p">=</span> <span class="kc">nil</span>
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<span class="nx">t3</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="nx">s</span><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>Using a range action you can loop through a slice.
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Each time the range block is getting executed dot will be set
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to current item of slice.</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="nx">t4</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">template</span><span class="p">.</span>
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<span class="nf">New</span><span class="p">(</span><span class="s">"t4"</span><span class="p">).</span>
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<span class="nf">Parse</span><span class="p">(</span><span class="s">`Range: </span><span class="cp">{{</span><span class="w"> </span><span class="k">range</span><span class="w"> </span><span class="na">.</span><span class="w"> </span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="na">.</span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="cp">}}</span><span class="s">`</span><span class="p">)</span>
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<span class="nx">t4</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span>
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<span class="p">[]</span><span class="kt">string</span><span class="p">{</span>
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<span class="s">"Go"</span><span class="p">,</span>
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<span class="s">"Rust"</span><span class="p">,</span>
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<span class="s">"C++"</span><span class="p">,</span>
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<span class="s">"C#"</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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<tr>
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<td class="docs">
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<p>You can assign and reassign a value to a variable in templates.</p>
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</td>
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<td class="code">
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<pre class="chroma">
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<span class="nx">t5</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">template</span><span class="p">.</span>
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<span class="nf">New</span><span class="p">(</span><span class="s">"t5"</span><span class="p">).</span>
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<span class="nf">Parse</span><span class="p">(</span><span class="s">`Variables: </span><span class="cp">{{</span><span class="w"> </span><span class="nx">$language</span><span class="w"> </span><span class="o">:=</span><span class="w"> </span><span class="s">"go"</span><span class="w"> </span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="nx">$language</span><span class="w"> </span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="nx">$language</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"C"</span><span class="w"> </span><span class="cp">}}</span><span class="s">
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</span><span class="s"> </span><span class="cp">{{</span><span class="w"> </span><span class="nx">$language</span><span class="w"> </span><span class="cp">}}</span><span class="s">`</span><span class="p">)</span>
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<span class="nx">t5</span><span class="p">.</span><span class="nf">Execute</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">,</span> <span class="kc">nil</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 leading">
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<pre class="chroma"><span class="gp">$</span> go run templates.go
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<span class="go">Value is my-template
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</span><span class="go">Value is some text
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</span><span class="go">Value is true
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</span><span class="go">Value is 5
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</span><span class="go">Value is [Go Rust C++ C#]
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</span><span class="go">Value is {Jane Doe}
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</span><span class="go">Fullname: Jane Doe
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</span><span class="go">Fullname: Mickey Mouse</span></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="go"> Else block</span></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="go"> Else if block => Some text
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</span><span class="go">Range:
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</span><span class="go"> Go</span></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="go"> Rust</span></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="go"> C++</span></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="go"> C#
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</span><span class="go">Variables:
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</span><span class="go">go
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</span><span class="go">C</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="json">JSON</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 (\u000A \"log\"\u000A \"os\"\u000A \"text/template\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' t1 :\u003D template.New(\"t1\")\u000A');codeLines.push(' t1, err :\u003D t1.Parse(\"Value is {{.}}\\n\")\u000A if err !\u003D nil {\u000A log.Fatal(err)\u000A }\u000A');codeLines.push(' t1 \u003D template.Must(t1.Parse(\"Value is {{.}}\\n\"))\u000A');codeLines.push(' t1.Execute(os.Stdout, t1.Name())\u000A t1.Execute(os.Stdout, \"some text\")\u000A t1.Execute(os.Stdout, true)\u000A t1.Execute(os.Stdout, 5)\u000A t1.Execute(os.Stdout, []string{\u000A \"Go\",\u000A \"Rust\",\u000A \"C++\",\u000A \"C#\",\u000A })\u000A t1.Execute(os.Stdout, struct{ name string }{\u000A name: \"Jane Doe\",\u000A })\u000A');codeLines.push(' t2, _ :\u003D template.\u000A New(\"t2\").\u000A Parse(\"Fullname: {{.Fullname}}\\n\")\u000A');codeLines.push(' t2.Execute(os.Stdout, struct {\u000A Fullname string\u000A }{\u000A Fullname: \"Jane Doe\",\u000A })\u000A');codeLines.push(' t2.Execute(os.Stdout, map[string]string{\u000A \"Fullname\": \"Mickey Mouse\",\u000A })\u000A');codeLines.push(' t3, _ :\u003D template.\u000A New(\"t3\").\u000A Parse(`{{if .Field1}}\u000A If block \u003D\u003E {{.Field1}}\u000A {{ else if .Field2}}\u000A Else if block \u003D\u003E {{.Field2}}\u000A {{ else }}\u000A Else block\u000A {{ end }}`)\u000A');codeLines.push(' s :\u003D struct {\u000A Field1 string\u000A Field2 []string\u000A }{}\u000A');codeLines.push(' s.Field1 \u003D \"\"\u000A s.Field2 \u003D []string{}\u000A t3.Execute(os.Stdout, s)\u000A');codeLines.push(' s.Field1 \u003D \"Some text\"\u000A s.Field2 \u003D nil\u000A t3.Execute(os.Stdout, s)\u000A');codeLines.push(' t4, _ :\u003D template.\u000A New(\"t4\").\u000A Parse(`Range: {{ range . }}\u000A {{.}}\u000A {{ end }}`)\u000A t4.Execute(os.Stdout,\u000A []string{\u000A \"Go\",\u000A \"Rust\",\u000A \"C++\",\u000A \"C#\",\u000A })\u000A');codeLines.push(' t5, _ :\u003D template.\u000A New(\"t5\").\u000A Parse(`Variables: {{ $language :\u003D \"go\" }}\u000A {{ $language }}\u000A {{ $language \u003D \"C\" }}\u000A {{ $language }}`)\u000A t5.Execute(os.Stdout, nil)\u000A}\u000A');codeLines.push('');codeLines.push('');codeLines.push('');codeLines.push('');codeLines.push('');codeLines.push('');
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</script>
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<script src="site.js" async></script>
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