title: What evaluates to false in Ruby?
body: <p><code>false</code> and <code>nil</code> evaluate to <strong>false</strong> in <code>Ruby</code>. Anything else? Please provide links to official/authoritative references.</p>
  
  <pre><code>2.0.0p247 :001 &gt; if true ; puts 'TRUE' ; else puts 'FALSE' ; end
  TRUE
  
  2.0.0p247 :002 &gt; if false ; puts 'TRUE' ; else puts 'FALSE' ; end
  FALSE
  
  2.0.0p247 :003 &gt; if nil ; puts 'TRUE' ; else puts 'FALSE' ; end
  FALSE
  
  2.0.0p247 :004 &gt; if 0 ; puts 'TRUE' ; else puts 'FALSE' ; end
  TRUE
  
  2.0.0p247 :005 &gt; if [] ; puts 'TRUE' ; else puts 'FALSE' ; end
  TRUE
  
  2.0.0p247 :006 &gt; if {} ; puts 'TRUE' ; else puts 'FALSE' ; end
  TRUE
  
  2.0.0p247 :007 &gt; if '' ; puts 'TRUE' ; else puts 'FALSE' ; end
  (irb):616: warning: string literal in condition
  TRUE
  </code></pre>