title: Select first element of nested list
body: <p>Let's say I have a list like this:</p>
  
  <pre><code>x = list(list(1,2), list(3,4), list(5,6))
  </code></pre>
  
  <p>I would like a list that contains only the first elements of the nested list. I can do this by returning another list like so</p>
  
  <pre><code>x1 = lapply(x, function(l) l[[1]])
  </code></pre>
  
  <p>Is there shortcut notation for this?</p>