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Date: Mon, 04 Sep 2006 09:22:26 +0200
From: Alain Frisch <Alain.Frisch@inria.fr>
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To: oleg@pobox.com
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Eliminating array bounds check
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X-Spam: no; 0.00; frisch:01 frisch:01 oleg:01 oleg:01 sig:01 val:01 struct:01 ocaml:01 functors:01 applicative:01 ocaml:01 functor:01 sig:01 val:01 struct:01 

Hello Oleg,

oleg@pobox.com wrote:
> For example:
>  http://pobox.com/~oleg/ftp/ML/eliminating-array-bound-check-literally.ml

>>From your code:
=======================================
(* First, we, on off-chance, check if we can obtain type
   eigen-variables via the module system.
*)

module GenT : sig type t val v : t end =
  struct type t = int let v = 1 end
;;
let module M1 = GenT in
let module M2 = GenT in
M1.v = M2.v
;;

(* Alas, the latter succeeds and reports no type error. What did we
   expect: OCaml functors are applicative.
   Fortunately, OCaml supports higher-rank types.
*)
=======================================

What about making GenT a functor and passing it unnamed structures as
arguments? (Ok, you must then trust the client not to apply GenT with
named structures.)

module GenT(X:sig end) : sig type t val v : t end =
  struct type t = int let v = 1 end
;;
let module M1 = GenT(struct end) in
let module M2 = GenT(struct end) in
M1.v = M2.v
;;

You could then simplify the TrustedKernel so as not to use polymorphic
record fields (and also to use a direct style instead of a continuation
style for brand).


-- Alain