constants

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Go by Example: Constants</title>
    <link rel=stylesheet href="site.css">
  </head>
  <script type="text/javascript">
    if (window.location.host == "gobyexample.com") {
      var _gaq = _gaq || [];
      _gaq.push(['_setAccount', 'UA-34996217-1']);
      _gaq.push(['_trackPageview']);
      (function() {
        var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
        ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
        var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
      })();
    }
  </script>
  <body>
    <div class="example" id="constants">
      <h2><a href="./">Go by Example</a>: Constants</h2>

      <table>

        <tr>
          <td class="docs">
            <p>Go supports <em>constants</em> of character, string, boolean,
and numeric values.</p>

          </td>
          <td class="code empty leading">


          </td>
        </tr>

        <tr>
          <td class="docs">

          </td>
          <td class="code leading">
	        <a href="http://play.golang.org/p/T5sj0eINnp"><img title="Run code" src="play.png" class="run" /></a>
            <div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">

          </td>
          <td class="code leading">

            <div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;fmt&quot;</span>
<span class="kn">import</span> <span class="s">&quot;math&quot;</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p><code>const</code> declares a constant value.</p>

          </td>
          <td class="code leading">

            <div class="highlight"><pre><span class="kd">const</span> <span class="nx">s</span> <span class="kt">string</span> <span class="p">=</span> <span class="s">&quot;constant&quot;</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">

          </td>
          <td class="code leading">

            <div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">s</span><span class="p">)</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p>A <code>const</code> statement can appear anywhere a <code>var</code>
statement can.</p>

          </td>
          <td class="code leading">

            <div class="highlight"><pre>    <span class="kd">const</span> <span class="nx">n</span> <span class="p">=</span> <span class="mi">500000000</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p>Constant expressions perform arithmetic with
arbitrary precision.</p>

          </td>
          <td class="code leading">

            <div class="highlight"><pre>    <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>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p>A numeric constant has no type until it&rsquo;s given
one, such as by an explicit cast.</p>

          </td>
          <td class="code leading">

            <div class="highlight"><pre>    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">int64</span><span class="p">(</span><span class="nx">d</span><span class="p">))</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p>A number can be given a type by using it in a
context that requires one, such as a variable
assignment or function call. For example, here
<code>math.Sin</code> expects a <code>float64</code>.</p>

          </td>
          <td class="code">

            <div class="highlight"><pre>    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">math</span><span class="p">.</span><span class="nx">Sin</span><span class="p">(</span><span class="nx">n</span><span class="p">))</span>
<span class="p">}</span>
</pre></div>

          </td>
        </tr>

      </table>

      <table>

        <tr>
          <td class="docs">

          </td>
          <td class="code">

            <div class="highlight"><pre><span class="gp">$</span> go run constant.go
<span class="go">constant</span>
<span class="go">6e+11</span>
<span class="go">600000000000</span>
<span class="go">-0.28470407323754404</span>
</pre></div>

          </td>
        </tr>

      </table>


      <p class="next">
        Next example: <a href="for">For</a>.
      </p>

      <p class="footer">
        by <a href="https://twitter.com/mmcgrana">@mmcgrana</a> | <a href="mailto:mmcgrana@gmail.com">feedback</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/constants">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
      </p>
    </div>
  </body>
</html>