From: Remi VANICAT <vanicat@labri.u-bordeaux.fr>
To: caml-list@inria.fr
Subject: Re: [Caml-list] static variables in a function
Date: Mon, 17 Jun 2002 01:19:21 +0200 [thread overview]
Message-ID: <87k7oyreva.dlv@wanadoo.fr> (raw)
In-Reply-To: <20020616021902.A22564@max.home> (Max Kirillov's message of "Sun, 16 Jun 2002 02:19:02 +0700")
Max Kirillov <max630@mail.ru> writes:
> On Sat, Jun 15, 2002 at 12:14:09PM -0400, John Prevost wrote:
> <...>
>> If we change our focus, howeverm the technique becomes more
>> interesting. Take a look at this, for example:
> <...>
>> let memoize f =
>
> Hmm... this isn't executed at read time because function has
> a parameter...
this code :
let memoize f =
let stow = Hashtbl.create 20 in
fun x -> begin
if not (Hashtbl.mem stow x) then begin
try (let v = f x in Hashtbl.replace stow x (Val v))
with e -> Hashtbl.replace stow x (Exn e)
end;
match Hashtbl.find stow x with
| Val x -> x
| Exn e -> raise e
end
was correct :
it create a new Hastable for each different function one want to
memoize. Otherwise the hastable will be shared between different
function, what we realy don't want.
look at this for a proof of what I'm saying :
# let print_once = memoize print_endline;;
val print_once : string -> unit = <fun>
# print_once "foo";;
foo
- : unit = ()
# print_once "bar";;
bar
- : unit = ()
# print_once "bar";;
- : unit = ()
#
the last time, the value isn't recompile (and then nothing is
printed), so the memoization have worked.
--
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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next prev parent reply other threads:[~2002-06-16 23:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-14 17:08 Shannon --jj Behrens
2002-06-14 17:40 ` Stefano Zacchiroli
2002-06-14 17:58 ` Yutaka OIWA
2002-06-14 20:43 ` Shannon --jj Behrens
2002-06-15 4:42 ` Max Kirillov
2002-06-15 6:36 ` John Prevost
2002-06-15 14:51 ` Max Kirillov
2002-06-15 16:14 ` John Prevost
2002-06-15 19:19 ` Max Kirillov
2002-06-15 23:16 ` John Prevost
2002-06-16 23:19 ` Remi VANICAT [this message]
2002-06-17 13:56 ` [Caml-list] Memoizing (was: static variables...) Benedikt Rosenau
2002-06-18 8:40 ` William Lovas
2002-06-18 9:16 ` Jacek Chrzaszcz
2002-06-18 21:52 ` William Lovas
2002-06-18 13:07 ` Christopher Quinn
2002-06-18 14:07 ` Remi VANICAT
2002-06-18 17:52 ` Christopher Quinn
2002-06-19 14:42 ` John Max Skaller
2002-06-23 21:18 ` Pierre Weis
2002-06-19 4:38 ` [Caml-list] static variables in a function Shannon --jj Behrens
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