gcc/m2/gm2-libs-log/Random.mod

(* Random.mod provides a Logitech-3.0 compatible library.

Copyright (C) 2005-2026 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius.mulley@southwales.ac.uk>.

This file is part of GNU Modula-2.

GNU Modula-2 is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GNU Modula-2 is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  *)

IMPLEMENTATION MODULE Random ;

FROM libc IMPORT rand, srand ;
FROM Selective IMPORT Timeval, InitTime, KillTime, GetTime, GetTimeOfDay ;


(*
   Randomize - initialize the random number generator with a seed
               based on the microseconds.
*)

PROCEDURE Randomize ;
VAR
   t        : Timeval ;
   sec, usec: CARDINAL ;
BEGIN
   t := InitTime (0, 0) ;
   IF GetTimeOfDay (t) = 0
   THEN
   END ;
   GetTime (t, sec, usec) ;
   RandomInit (usec) ;
   t := KillTime (t)
END Randomize ;


(*
   RandomInit - initialize the random number generator with value, seed.
*)

PROCEDURE RandomInit (seed: CARDINAL) ;
BEGIN
   srand (seed)
END RandomInit ;


(*
   RandomBytes - fills in an array with random values.
*)

PROCEDURE RandomBytes (VAR a: ARRAY OF BYTE) ;
VAR
   i, h: CARDINAL ;
BEGIN
   h := HIGH (a) ;
   i := 0 ;
   WHILE i <= h DO
      a[i] := VAL (BYTE, rand ()) ;
      INC (i)
   END
END RandomBytes ;


(*
   RandomInt - return an INTEGER in the range 0..bound-1
*)

PROCEDURE RandomInt (bound: INTEGER) : INTEGER ;
BEGIN
   IF bound=0
   THEN
      RETURN rand ()
   ELSE
      RETURN rand () MOD bound
   END
END RandomInt ;


(*
   RandomCard - return a CARDINAL in the range 0..bound-1
*)

PROCEDURE RandomCard (bound: CARDINAL) : CARDINAL ;
VAR
   c: CARDINAL ;
BEGIN
   RandomBytes (c) ;
   RETURN c MOD bound
END RandomCard ;


(*
   RandomReal - return a REAL number in the range 0.0..1.0
*)

PROCEDURE RandomReal () : REAL ;
BEGIN
   RETURN RandomLongReal ()
END RandomReal ;


(*
   RandomLongReal - return a LONGREAL number in the range 0.0..1.0
*)

PROCEDURE RandomLongReal () : LONGREAL ;
VAR
   l: LONGCARD ;
BEGIN
   RandomBytes (l) ;
   RETURN VAL (LONGREAL, l) / VAL (LONGREAL, MAX (LONGCARD))
END RandomLongReal ;


BEGIN
   Randomize
END Random.