title: uninitialized constant bigdecimal (nameerror)
body: <pre><code>val = BigDecimal.new("0")
  </code></pre>
  
  <p>Running this statement shows uninitialized constant bigdecimal (nameerror) error.  </p>
  
  <p>Then modifying to:  </p>
  
  <pre><code>require "bigdecimal"
  val = BigDecimal.new("0")
  </code></pre>
  
  <p>That's ok.
  BigDecimal belongs to Ruby Standard Library. So I need to <code>require 'bigdecimal'</code>?  </p>
  
  <p><strong>Question:</strong>  </p>
  
  <ul>
  <li>Where is <code>BigDecimal</code> defined?   </li>
  <li>What's the definition file? I didn't find the file in lib folder.</li>
  </ul>