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|
-- This file is free software, which comes along with SmartEiffel. This
-- software 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. You can modify it as you want, provided
-- this header is kept unaltered, and a notification of the changes is added.
-- You are allowed to redistribute it and sell it, alone or as a part of
-- another product.
-- Copyright (C) 1994-98 LORIA - UHP - CRIN - INRIA - FRANCE
-- Dominique COLNET and Suzanne COLLIN - colnet@loria.fr
-- http://www.loria.fr/SmartEiffel
--
class STD_RAND
-- Press' standard generator, which uses the minimal standard
-- and then uses shuffling to break up short order corelations.
creation with_seed
feature {NONE}
seed:INTEGER
ia: INTEGER is 16807;
im: INTEGER is 2147483647;
iq: INTEGER is 127773;
ir: INTEGER is 2836;
iv: ARRAY[INTEGER];
ntab: INTEGER is 32;
iy: INTEGER;
feature {NONE}
min_next is
local
k: INTEGER;
do
k := seed // iq;
seed := ia * (seed -k * iq) - ir * k;
if seed < 0 then
seed := seed + im;
end;
end;
with_seed(seed_value:INTEGER) is
require
valid_seed: seed_value > 0 and seed_value < im
local
i: INTEGER;
do
seed := seed_value;
min_next;
!!iv.make(1,ntab);
from
i := 1;
until
i > 7
loop
min_next;
i := i + 1;
end;
from
i := ntab;
until
i = 0
loop
iv.put(seed,i);
min_next;
i := i - 1;
end
iy := iv.item(1);
next;
end
feature
next is
local
tmp:INTEGER
do
tmp := iy \\ ntab + 1;
min_next;
iy := iv.item(tmp);
iv.put(seed,tmp);
end
last_integer(n:INTEGER):INTEGER is
do
Result := iy \\ n + 1;
end
end -- STD_RAND
|
