ruberon/samples/Windows/Console/exp.ob07

(*
   adapted to Oberon-07 by 0CodErr, KolibriOS team
                                                   *)
(* Print first 'PRINT' digits of 'e'.
 *
 * Originally written in Pascal by Scott Hemphill
 * Rewritten in Modula-2 and modified by Andrew Cadach
 *
 *)

MODULE exp;

IMPORT In, Out, Console;


CONST
    PRINT = 1024;
    DIGITS = PRINT + (PRINT + 31) DIV 32;


TYPE
    number = ARRAY DIGITS + 1 OF INTEGER;


VAR
    s, x: number;
    xs, i: INTEGER;


PROCEDURE init (VAR x: number; n: INTEGER);
VAR
    i: INTEGER;

BEGIN
    x[0] := n;
    FOR i := 1 TO DIGITS DO x[i] := 0 END
END init;


PROCEDURE divide (VAR x: number; xs, n: INTEGER;
                  VAR y: number; VAR ys: INTEGER);
VAR
    i, c: INTEGER;

BEGIN
    c := 0;
    FOR i := xs TO DIGITS DO
        c := 10 * c + x[i];
        y[i] := c DIV n;
        c := c MOD n
    END;
    ys := xs;
    WHILE (ys <= DIGITS) & (y[ys] = 0) DO INC(ys) END
END divide;


PROCEDURE add (VAR s, x: number; xs: INTEGER);
VAR
    i, c: INTEGER;
BEGIN
    c := 0;
    FOR i := DIGITS TO xs BY -1 DO
        c := c + s[i] + x[i];
        IF c >= 10 THEN
            s[i] := c - 10;
            c := 1
        ELSE
            s[i] := c;
            c := 0
        END
    END;
    i := xs;
    WHILE c # 0 DO
        DEC(i);
        c := c + s[i];
        IF c >= 10 THEN
            s[i] := c - 10;
            c := 1
        ELSE
            s[i] := c;
            c := 0
        END
    END
END add;


BEGIN
    Console.open;

    init(s, 0);
    init(x, 1);
    xs := 0;
    add(s, x, xs);
    i := 0;
    REPEAT
        INC(i);
        divide(x, xs, i, x, xs);
        add(s, x, xs);
    UNTIL xs > DIGITS;
    Out.Ln;
    Out.String ("   e = ");
    Out.Char (CHR(s[0] + ORD("0")));
    Out.Char (".");
    FOR i := 1 TO PRINT DO
        Out.Char (CHR(s[i] + ORD("0")));
        IF i MOD 64 = 0 THEN
            Out.Ln;
            Out.Int (i, 5);
            Out.String ("    ")
        END
    END;
    Out.Ln;
    Out.Ln;
    In.Ln;

    Console.exit(TRUE)
END exp.