title: Scalaz Lens to ReaderWriterState
body: <p>Given, say</p>
  
  <pre><code>case class Person(age: Int)
  val ageL: Lens[Person, Int] = ...
  </code></pre>
  
  <p>How do I come up with:</p>
  
  <pre><code>def incrementAge(by: Int): ReaderWriterState[Config, String, Person]
  </code></pre>
  
  <p>while taking advantage of <code>ageL</code> lens. The Scalaz Lens have some utilities to create a <code>State</code> out of a <code>Lens</code>, but I'm not sure how to convert that to a <code>ReaderWriterState</code>.</p>