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redo random-bytes* with a better algorithm

db4
Doug Coleman 2008-11-12 22:10:34 -06:00
parent 8f6f666a2a
commit db2f744f90
1 changed files with 8 additions and 14 deletions
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22
basis/random/random.factor
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@ -13,17 +13,13 @@ GENERIC: seed-random ( tuple seed -- )
GENERIC: random-32* ( tuple -- r )
GENERIC: random-bytes* ( n tuple -- byte-array )
<PRIVATE
: adjust-random ( n m -- n' )
3 mask zero? [ 1+ ] unless ; inline
PRIVATE>
M: object random-bytes* ( n tuple -- byte-array )
[ [ 4 /i ] keep adjust-random ] dip
over 4 * <byte-vector>
[ '[ _ random-32* 4 >le _ push-all ] times ] keep ;
[ [ <byte-vector> ] keep 4 /mod ] dip tuck
[ pick '[ _ random-32* 4 >le _ push-all ] times ]
[
over zero?
[ 2drop ] [ random-32* 4 >le swap head over push-all ] if
] 2bi* ;
M: object random-32* ( tuple -- r ) 4 random-bytes* le> ;
@ -37,15 +33,13 @@ M: f random-bytes* ( n obj -- * ) no-random-number-generator ;
M: f random-32* ( obj -- * ) no-random-number-generator ;
: random-bytes ( n -- byte-array )
[
dup adjust-random random-generator get random-bytes*
] keep head-slice >byte-array ;
random-generator get random-bytes* ;
<PRIVATE
: random-integer ( n -- n' )
dup log2 7 + 8 /i 1+
[ random-bytes byte-array>bignum ]
[ random-bytes >byte-array byte-array>bignum ]
[ 3 shift 2^ ] bi / * >integer ;
PRIVATE>