(         Title:  Random Number Generator
           File:  ren.fs
        Version:  0.9.0
Original Author:  W. J. Cody, 1987
      Ported by:  David N. Williams
        License:  ACM noncommercial use
  Starting date:  January 10, 2003
  Last revision:  January 10, 2003

This is a port of W. J. Cody's REN subprogram in the celefunt
package, from Fortran 77 to ANS Forth.  As ACM Algorithm 714
[TOMS], the celefunt package is presumed to be under the ACM
license for noncommercial use:

http://www.acm.org/pubs/copyright_policy/softwareCRnotice.html

There is an ANS Forth environmental dependence on lower case.

Quote from the original celefunt package:

  Random number generator -- based on Algorithm 266 by Pike and
  Hill [modified by Hansson], Communications of the ACM, Vol. 8,
  No. 10, October 1965.

  This subprogram is intended for use on computers with fixed
  point wordlength of at least 29 bits.  It is best if the
  floating-point significand has at most 29 bits.

  Latest revision - March 19, 1987

  Author - W. J. Cody
           Argonne National Laboratory
)

decimal
s" FLOATING-EXT"   environment? [IF] ( flag) drop
s" FLOATING-STACK" environment? [IF] ( maxdepth) drop

100001 value iy  \ seed the random number

: ren  ( f: -- r )
  iy 125 *                    ( IY=IY*125)
  dup 2796203 / 2796203 * -   ( IY=IY-[IY/2796203]*2796203)
  dup to iy   0 d>f           ( f: FY=CONV[IY]) 
  2796203E f/ 1E 1E-6 f+
      1E-12 f+ f*             ( f: FY/C1*[1+C2+C3])
;

[ELSE] .( ***Separate floating point stack not available.) [THEN]
[ELSE] .( ***Floating point not available.)                [THEN]