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Date: -- (:)
From: Vincent Balat [prof Moggi team] <balat@d...>
Subject: Re: [Caml-list] partial eval question

I am working on a "type-directed" partial evaluator for OCaml.
I did an implementation a few years ago with Olivier Danvy
(see http://www.pps.jussieu.fr/~balat/publications/balat-danvy.pdf)

But it is still*experimental*:
 - only a small subset on ocaml
 - need a modified version of ocaml with a "call/cc" operator

ex:
# let rec power mul one x n = 
      if n=0 then one 
      else (mul x (power mul one x (n-1)));;  
      (* We close by mul and one because the function to be
         normalized must be mostly polymorphic *)
val power : ('a -> 'b -> 'b) -> 'b -> 'a -> int -> 'b = <fun>

# let power3 mul one x = power mul one x 3;;
val power3 : ('a -> 'b -> 'b) -> 'b -> 'a -> 'b = <fun>

# normalize "power3";;
- : unit = ()
(* Now the function power3 is normalized *)

(* You can print the normalized code by: *)
# normalize_nf "power3";;
- : NormalForms.computation =
(fun v7 v8 v9 ->
 let v10 = v7 v9 in
 let v11 = v10 v8 in
 let v12 = v7 v9 in
 let v13 = v12 v11 in
 let v14 = v7 v9 in
 let v15 = v14 v13 in
 v15)

It is not available on the web  any more (it was for ocaml 1.05) but I
can send it to you if you are interested.

I'm planning to update  it and to try to extend it  to a larger subset
of ocaml.  There are still a  lot of opened questions  to solve before
having it included in ocaml...

Otherwise,  as  pointed  by  Damien  Pous,  you can  have  a  look  at
MetaOCaml, which is  a multi-level language based on  ocaml, that is a
language  that   allows  you   to  manipulate  source   code  (program
generation).

Vincent Balat

---- Ben Kavanagh écrit :
 > 
 > Say I have a function such as pow defined as
 > 
 > let pow n x = 
 >     let rec pow_iter (n1, x1, p1) = 
 >         if (n1 = 0) then p1 
 >         else if (n1 mod 2 = 0) 
 > 		 then pow_iter(n1/2, x1*x1, p1) 
 >              else pow_iter(n1-1, x1, p1*x1)
 >     in pow_iter(n, x, 1);;
 > 
 > and I say 
 > 
 > let pow2 = pow 2
 > 
 > Are there any ML implementations that would automatically perform
 > partial evaluation to create pow2 instead of using closures, possibly
 > unfolding the pow_iter call? Would Caml ever have this capability?
 > 
 > Ben
 > 
 > 
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