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From: Yann =?iso-8859-1?q?R=E9gis-Gianas?= <yann@lrde.epita.fr> (by way of Yann =?iso-8859-1?q?R=E9gis-Gianas?= <yann@lrde.epita.fr>)
Organization: LRDE
Subject: Re: [Caml-list] arbitrarily large integers
Date: Tue, 3 Dec 2002 10:47:09 +0100
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Le Mardi 3 D=E9cembre 2002 08:40, Scott J. a =E9crit :
> Hi,

=09Hello,

> is it possible to implement in OCamel arbitrary large integers as
> in Dolphin smalltalk e.g. where e.g. factorial 10000 is evaluated
> very fast

=09Yes, it's possible : just use the nums library (documented in the
documentation at http://caml.inria.fr/ocaml/htmlman/manual036.html).

=09An example :

#load "nums.cma";;

(* directly with Big_int ... *)
open Big_int

let fact n =3D
  let rec fact_ acu p =3D
    if p =3D zero_big_int then
      acu
    else
      fact_ (mult_big_int acu p) (sub_big_int p unit_big_int)
  in
  fact_ unit_big_int n;;

string_of_big_int (fact (big_int_of_int 10000));;

(* more convenient with Num. *)

open Num

let n_ =3D num_of_int

let big_fact n =3D
  let rec fact_ acu p =3D
    if p =3D n_ 0 then
      acu
    else
      fact_ (acu */ p) (p -/ (n_ 1))
  in
  fact_ (n_ 1) n;;

string_of_num (big_fact (n_ 10000))


--
Yann Regis-Gianas
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