189 lines
6.3 KiB
Plaintext
Generated
189 lines
6.3 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 Em Exemplos: Constants</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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if (e.key == "ArrowLeft") {
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<div class="example" id="constants">
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<h2><a href="./">Go by Example</a>: Constants</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Go suporta <em>constantes</em> de tipos strings, booleanos,
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e numericos.</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 target="_blank" href="https://go.dev/play/p/NA0z_34sqzx"><img title="Executar código em nova aba" src="play.png" class="run" /></a><img title="Copiar código" 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="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"math"</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><code>const</code> é a palavra reservada para declarar uma constante.</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">const</span> <span class="nx">s</span> <span class="kt">string</span> <span class="p">=</span> <span class="s">"constant"</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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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</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>A declaração <code>const</code> pode aparecer em qualquer
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lugar que a declaração <code>var</code> também possa.</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">const</span> <span class="nx">n</span> <span class="p">=</span> <span class="mi">500000000</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>Expressões com constantes são performadas
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aritmeticamente com precisão arbitrária.</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">const</span> <span class="nx">d</span> <span class="p">=</span> <span class="mf">3e20</span> <span class="o">/</span> <span class="nx">n</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="nx">d</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>Uma constante numérica não possui um tipo
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até que seja atribuído um, como uma conversão explícita.</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">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">int64</span><span class="p">(</span><span class="nx">d</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>Um tipo pode ser implicitamente atribuído a uma constante
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numérica ao usá-la num contexto que requer um tipo,
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como atribuição a uma variável ou uma chamada de função.
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Por exemplo, a função <code>math.Sin</code> espera um valor de tipo
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<code>float64</code>.</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">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">math</span><span class="p">.</span><span class="nf">Sin</span><span class="p">(</span><span class="nx">n</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 constant.go
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<span class="go">constant
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</span><span class="go">6e+11
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</span><span class="go">600000000000
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</span><span class="go">-0.28470407323754404</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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Próximo exemplo: <a href="for">For</a>.
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</p>
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<p class="footer">
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Por <a href="https://markmcgranaghan.com">Mark McGranaghan</a> e <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | traduzido por <a href="https://github.com/lucassauro">Lucassauro</a> | <a href="https://github.com/lucassauro/gobyexample">contribua</a> | <a href="https://github.com/mmcgrana/gobyexample#license">licença</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 \"fmt\"\u000A \"math\"\u000A)\u000A');codeLines.push('const s string \u003D \"constant\"\u000A');codeLines.push('func main() {\u000A fmt.Println(s)\u000A');codeLines.push(' const n \u003D 500000000\u000A');codeLines.push(' const d \u003D 3e20 / n\u000A fmt.Println(d)\u000A');codeLines.push(' fmt.Println(int64(d))\u000A');codeLines.push(' fmt.Println(math.Sin(n))\u000A}\u000A');codeLines.push('');
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