Difference between revisions of "Delphi compatible LCG Random"

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Here are cross-platform functions that generate Delphi-identical pseudo-random numbers:
 
Here are cross-platform functions that generate Delphi-identical pseudo-random numbers:
 
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unit lcgrandom;
+
unit lcg_random;
 
// Delphi compatible LCG random number generator routines for Freepascal.
 
// Delphi compatible LCG random number generator routines for Freepascal.
 
// (c)2017, Thaddy de Koning. Use as you like
 
// (c)2017, Thaddy de Koning. Use as you like

Revision as of 16:40, 26 March 2017

Delphi compatible random numbers

Many Freepascal programmers also maintain sourcecode in Delphi.
Even if you have moved to Freepascal from Delphi you may have data that relies on Delphi's Random.
Here are cross-platform functions that generate Delphi-identical pseudo-random numbers:

unit lcg_random;
// Delphi compatible LCG random number generator routines for Freepascal.
// (c)2017, Thaddy de Koning. Use as you like
// Algorithm, Delphi multiplier and increment taken from:
// https://en.wikipedia.org/wiki/Linear_congruential_generator
// The default Delphi RandomSeed is determined as zero.
{$mode objfpc}

interface

function LCGRandom: extended; overload;inline;
function LCGRandom(const range:longint):longint;overload;inline;

implementation

function IM:cardinal;inline;
begin
  RandSeed := RandSeed * 134775813  + 1;
  Result := RandSeed;
end;

function LCGRandom: extended; overload;inline;
begin
  Result := IM * 2.32830643653870e-10;
end;

function LCGRandom(const range:longint):longint;overload;inline;
begin
  Result := IM * range shr 32;
end;

end.