title: ocaml type missmatch unit vs list
body: <p>For this signature </p>
  
  <pre><code>val chooser: string list * string list -&gt; string list
  </code></pre>
  
  <p>and this implementation </p>
  
  <pre><code> let rec chooser (inputList, trueList) = match inputList with
        [] -&gt; []
      | iH::iT -&gt; if (List.hd trueList)="True" 
          then iH::(chooser iT List.tl trueList)
  </code></pre>
  
  <p>I am getting the following error: </p>
  
  <p>Error: This variant expression is expected to have type unit 
  The constructor :: does not belong to unit</p>
  
  <p>What am I doing wrong? </p>