Re: [Caml-list] Question on writing efficient Ocaml.

[Philippe Wang <lists@philippewang.info>]

Le 6 janv. 07 à 01:52, Nathaniel Gray a écrit :

> As Xavier points out, one can use modules to hide basic types, but
> this is pretty clumsy in practice.  There's rumored to be a solution
> using phantom types, but my attempts don't work:
>
> # type 'a boink = int;;
> type 'a boink = int
> # let f = (20 : string boink);;
> val f : string boink = 20
> # let g = (30 : int boink);;
> val g : int boink = 30
> # f;;
> - : string boink = 20
> # g;;
> - : int boink = 30
> # f + g;;
> - : int = 50

Hmmm... the expression
> f + g;;
becomes an int because ( + ) : int -> int -> int

If you write :

((+) : int -> int boink -> string boink) f g

instead, it may do what you meant to do...

Cheers,

Philippe Wang
    mail(at)philippewang.info