Difference between revisions of "Delphi compatible LCG Random"
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// https://en.wikipedia.org/wiki/Linear_congruential_generator | // https://en.wikipedia.org/wiki/Linear_congruential_generator | ||
// The default Delphi RandomSeed is determined as zero. | // The default Delphi RandomSeed is determined as zero. | ||
− | {$mode objfpc} | + | {$ifdef fpc}{$mode objfpc}{$endif} |
interface | interface |
Revision as of 19:59, 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 given the same RandSeed:
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.
{$ifdef fpc}{$mode objfpc}{$endif}
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.