um types. Each case
of the union corresponds to a constructor of the sum type. The
constructor is constant if the union case has no associated field,
otherwise has one argument corresponding to the union case field. If
the union has a <span class=machine><span class=font-tt>default</span></span> case, an extra constructor
<span class=machine><span class=font-tt>Default</span></span><span class=machine><span class=font-tt>_</span></span><span class=font-it>unionname</span> is added to the Caml sum type, carr