title: Selecting string elements in a list using integer elements from another list
body: <p>I'm going to use an example to explain my question because I'm not sure the best way to put it into words.</p>
  
  <p>Lets say I have two lists <code>a</code> and <code>b</code>:</p>
  
  <p><code>a = ["car", "bike", "train"]</code> and <code>b = [1, 3]</code></p>
  
  <p>And I want to create a new list <code>c</code> by selecting the items in <code>a</code> whose positions correspond to the integers in <code>b</code>, so list <code>c = ["car", "train"]</code></p>
  
  <p>How would I do this in Haskell? I think I have to use list comprehension but am unsure how. Cheers. </p>