kolibrios/programs/develop/oberon07/Samples/Windows/Console/fact.ob07

(*
   adapted to Oberon-07 by 0CodErr, KolibriOS team
                                                   *)
(*
 * Written by Andrew Cadach
 *
 * Recursive (extremely uneficient:-) implementation of factorial
 *
 *                     n * (n-1)!, n <> 0
 * By definition, n! =
 *                     1, n = 0
 *
 *)

MODULE fact;

IMPORT In, Out, Console;


CONST
    MAX_INTEGER = ROR(-2, 1);


VAR
    i, r: INTEGER;


PROCEDURE f (n: INTEGER): INTEGER;
VAR
    Res: INTEGER;

BEGIN
    IF n = 0 THEN
        Res := 1
    ELSE
        Res := n * f (n - 1)
    END

    RETURN Res
END f;


BEGIN
    Console.open;

    i := 0;
    REPEAT
        r := f(i);
        Out.String ("The factorial of ");
        Out.Int (i, 2);
        Out.String (" is ");
        Out.Int (r, 0);
        Out.Ln;
        INC(i)
    UNTIL r >= MAX_INTEGER DIV i;
    In.Ln;

    Console.exit(TRUE)
END fact.