title: How can I create a type with multiple parameters in OCaml?
body: <p>I'm trying to create a type that has multiple type parameters.  I know how to make a type with one parameter:</p>
  
  <pre><code>type 'a foo = 'a * int
  </code></pre>
  
  <p>But I need to have two parameters, so that I can parameterize the 'int' part.  How can I do this?</p>