title: OCaml: get value's type name
body: <p>Is is possible to print value's name in OCaml, for example if I have</p>
  
  <pre><code>type my_type =
    | MyType_First of int
    | MyType_Second of string
  </code></pre>
  
  <p>and then do something like:</p>
  
  <pre><code>let my_value = MyType_First 0 in
  print_string ("my_value is of type " ^ String.from_type my_value ^ ".\n";
  </code></pre>
  
  <p>can I get "my_value is of type MyType_First." ?</p>
  
  <p>Thank you.</p>