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math.combinatorics: faster nCk (use integer division).

db4
John Benediktsson 2013-04-06 11:43:20 -07:00
parent a52ee59005
commit d15dbaebb4
1 changed files with 2 additions and 1 deletions
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basis/math/combinatorics/combinatorics.factor
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@ -24,7 +24,7 @@ MEMO: factorial ( n -- n! )
2dup possible? [ dupd - [a,b) product ] [ 2drop 0 ] if ; 2dup possible? [ dupd - [a,b) product ] [ 2drop 0 ] if ;
: nCk ( n k -- nCk ) : nCk ( n k -- nCk )
twiddle [ nPk ] keep factorial / ; twiddle [ nPk ] keep factorial /i ;
! Factoradic-based permutation methodology ! Factoradic-based permutation methodology
@ -112,6 +112,7 @@ PRIVATE>
: next-permutation ( seq -- seq ) : next-permutation ( seq -- seq )
dup [ ] [ drop (next-permutation) ] if-empty ; dup [ ] [ drop (next-permutation) ] if-empty ;
! Combinadic-based combination methodology ! Combinadic-based combination methodology
<PRIVATE <PRIVATE