title: What does (string * string) list -> (string -> string) mean?
body: <p>This might be a super dumb question, but I don't get it.
  What does
  <code>(string * string) list -&gt; (string -&gt; string)</code> mean?
  Especially the last part <code>(string -&gt; string)</code>. How can you achieve that?</p>
  <p>I thought it'd be an inner function but it isn't I guess.</p>