title: Simple Ruby Proc with (&:)
body: <p>Quick question, I've run across this <code>select(&amp;:even)</code> syntax a few times, and I understand it for the most part except for one thing:</p>
  
  <p>The <code>&amp;</code> symbol, to me, is what makes the method name, well a method name. I don't understand why a symbol syntax is needed to define even. In a short example:</p>
  
  <pre><code>arr = [1,2,3,4,5]
  puts arr.select(&amp;:even?)
  </code></pre>
  
  <p>correctly selects and prints all the even numbers but,</p>
  
  <pre><code>arr = [1,2,3,4,5]
  puts arr.select(&amp;even?)
  </code></pre>
  
  <p>produces:</p>
  
  <p><code>Untitled 3.rb:2:in &lt;main&gt;: undefined method even? for main:Object (NoMethodError)
  </code></p>
  
  <p>Can anyone help me understand the necessity of using a <code>:</code> symbol?</p>