title: Fibonacci sequence in Ruby (recursion)
body: <p>I'm trying to implement the following function, but it keeps giving me the <code>stack level too deep (SystemStackError)</code> error.</p>
  
  <p>Any ideas what the problem might be ?</p>
  
  <pre><code>def fibonacci( n )
      [ n ] if ( 0..1 ).include? n
      ( fibonacci( n - 1 ) + fibonacci( n - 2 ) ) if n &gt; 1
  end
  
  puts fibonacci( 5 )
  </code></pre>