Re: [Caml-list] arbitrarily large integers

["Yann Régis-Gianas" <yann@lrde.epita.fr> (by way of Yann Régis-Gianas <yann@lrde.epita.fr>)]

Le Mardi 3 Décembre 2002 08:40, Scott J. a écrit :
> Hi,

	Hello,

> 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

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

	An example :

#load "nums.cma";;

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

let fact n =
  let rec fact_ acu p =
    if p = 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_ = num_of_int

let big_fact n =
  let rec fact_ acu p =
    if p = 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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