title: Haskell: fmap on nested functors
body: <p>What is the way to abstract mapping a function over a list of functors?</p>
  
  <p>I understand the basic applicative </p>
  
  <pre><code>λ: [(+2),(*2)] &lt;*&gt; [10,20]
  [12,22,20,40]
  </code></pre>
  
  <p>but how do I handle
  <code>[(+2),(*2)] ???? [Just 10, Just 20]</code>?</p>
  
  <p>all the ways I can think of seem really convoluted. </p>
  
  <p>for example:</p>
  
  <pre><code>λ: (&lt;$&gt;) &lt;$&gt; [(+2),(*2)]  &lt;*&gt; [Just 10, Just 20]
  [Just 12,Just 22,Just 20,Just 40]
  </code></pre>