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Message-ID: <4F399DD5.3000507@digirati.com.br>
Date: Mon, 13 Feb 2012 21:33:41 -0200
From: Andre Nathan <andre@digirati.com.br>
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Subject: [Caml-list] What am I reinventing here?

Hello

I have some code that behaves like the following.

module M = struct
   type ('a, 'b) ops = {
     bar_of_foo : 'a -> 'b;
     foo_of_bar : 'b -> 'a
   }

   let foo ops x = ops.bar_of_foo x
   let bar ops x = ops.foo_of_bar x
end

type foo = A | B
type bar = C | D

let ops = {
   M.bar_of_foo = (function A -> C | B -> D);
   M.foo_of_bar = (function C -> A | D -> B)
}

let () =
   match M.foo ops A with
   | C -> ()
   | D -> ()

The idea is to parametrize the behavior of some module M on two types 
and a set of operations involving these two types, with the catch that I 
want to keep the ability to pattern-match on the possible values of 
these types in the code that handles the return values from the 
functions exported by M.

With the scheme above I can do this, but passing a table of functions 
around doesn't look very nice. Is there any way I can use functors to do 
what this code does, while still being able to use pattern-matching? 
Would I have to resort to objects to be able to do this?

Thanks in advance,
Andre