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[Caml-list] dynamic runtime cast in Ocaml
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Date: 2002-11-08 (15:26)
From: Alain Frisch <frisch@c...>
Subject: Re: [Caml-list] dynamic runtime cast in Ocaml
On Thu, 7 Nov 2002, Jacques Garrigue wrote:

> By the way, for the expressivity addict (Curry-style), there is now a
> branch in CVS with support for a specific form of dependent types.

Nice !  Do you have specific cases of application in mind ?
It's amazing to see how Caml succeed in escaping ML jail (rows, HO
polymorphism, etc...).

> I plan to provide it as a patch after the next release.

Any long-term plan for inclusion in OCaml ?

I guess that backtracking unification could benefit to OCaml in other
places (e.g.:undoing the effect of typing an ill-typed expression in the

> and this without any overloading...

Well, you could also say that this is a lightweight solution for
overloading ...

Let's play a little bit ...

# fun x -> multimatch x with (a, `A x) -> (a,x) | (a, `B y) -> a + y;;
This expression has type int but is here used with type int * 'a

Mmm, need to rewrite it this way:

# fun x -> match x with (a, z) -> multimatch z with `A -> (a,x) | `B y -> a + y;;
- : (int * [< `A & 'b = int * 'a | `B of int & 'b = int] as 'a) -> 'b = <fun>

Do you have any paper/doc describing multimatch typing ?

-- Alain

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