title: OCaml: polymorphic function on maps with generic keys
body: <p>In OCaml, are there polymorphic function on generic maps? I.e:</p>
  
  <p>You can have: <code>f : 'a list -&gt; bool</code> as the equivalent to <code>bool f&lt;T&gt; ([T] x)</code></p>
  
  <p>Can you also have something like: <code>f : ('k,'v) map -&gt; bool</code> as the equivalent to <code>bool f&lt;K,V&gt; (Map&lt;K,V&gt; x)</code>?</p>
  
  <p>If so, what is the correct syntax of the type signature, and how do you implement such a function (I ask since map is an abstract type and the only way to manipulate it is to use functions that you get by calling <code>Map.Make</code> on a concrete type)?</p>
  
  <p>Thanks</p>