(*$I+ [include Pascal prgm stmts] *)
Program RandomDummy;
var SEED1, SEED2 : INTEGER;
(*
==============================================
PROGRAM TITLE: Random Number Generator
WRITTEN BY: Raymond E. Penley
DATE WRITTEN: 27 June 1980
WRITTEN FOR: Pascal/Z Users Group
SUMMARY:
Implements a Fibonacci series Random number generator.
RANDOM will return numbers from 0 to x
Call as Returns
------- ------------
real := RANDOM(10); 0.0 to 10.0
real := RANDOM(112); 0.0 to 112.0
I := TRUNC(RANDOM(10)); 0 to 10
Also within the body of the main program
but BEFORE calling RANDOM(X);
SEEDRAND;
==============================================
*)
PROCEDURE SEEDRAND;
(* INITIAL VALUES FOR SEED1 AND SEED2 ARE HERE *)
(*
NAME RANDOM
ENTRY SEEDRAND,RANDOM
SEEDRAND:
*)
Begin
SEED1 := 10946;
SEED2 := 17711
END;
Function Random(x: integer): real;
(*
GLOBAL
SEED1, SEED2 : INTEGER *)
CONST
factor = Maxint;
HALFINT = 16383; (* 1/2 OF MAXINT *)
VAR
x1 : real;
temp1, temp2, HALF_ADDER : INTEGER;
(*
RANDOM:
*)
Begin
(* Take 1/2 of the seeds for the comparison test *)
temp1 := SEED1 DIV 2;
temp2 := SEED2 DIV 2;
IF (temp1+temp2) >= HALFINT then{the number is too big -}
{ scale it down }
HALF_ADDER := temp1 + temp2 - HALFINT
ELSE
HALF_ADDER := temp1 + temp2;
SEED1 := SEED2;
(* Restore from previous DIVision *)
SEED2 := HALF_ADDER * 2;
(*---Convert X to real and divide by factor---*)
x1 := ((X*1.0)/factor);
(*---Return random number scaled by factor---*)
RANDOM := ( SEED2 * x1 );
End{ of RANDOM(X) };
(*$I- [turn off now] *)
