title: How do I make lenses from a record in GHCi
body: <p>I want to play around with the <code>Lens</code> library a bit.  I've loaded it into GHCi and created a record data type with the appropriate underscores:</p>
  
  <pre><code>&gt; data Foo a = Foo {_arg1 :: Int, _arg2 :: [a]}
  </code></pre>
  
  <p>I would like to make the lenses for <code>Foo</code> using the <code>makeLenses</code> template.  I would like to do this without needing to read through the entire set of <a href="http://www.haskell.org/haskellwiki/Template_Haskell">Template-Haskell docs</a>. </p>
  
  <p>What incantation can I type in at the GHCi prompt to get this to work?</p>