Combinations now map to input sequences directly

db4
Aaron Schaefer 2009-05-06 01:17:35 -04:00
parent 71022f9940
commit eaeda30bb1
1 changed files with 33 additions and 14 deletions

View File

@ -52,7 +52,7 @@ PRIVATE>
[ [ length factorial ] keep ] dip
'[ _ permutation @ ] each ; inline
: reduce-permutations ( seq initial quot -- result )
: reduce-permutations ( seq identity quot -- result )
swapd each-permutation ; inline
: inverse-permutation ( seq -- permutation )
@ -61,16 +61,13 @@ PRIVATE>
! Combinadic-based combination methodology
TUPLE: combination
{ n integer }
{ k integer } ;
C: <combination> combination
<PRIVATE
: dual-index ( combination m -- x )
[ [ n>> ] [ k>> ] bi nCk 1 - ] dip - ;
TUPLE: combo
{ seq sequence }
{ k integer } ;
C: <combo> combo
: largest-value ( a b x -- v )
#! TODO: use a binary search instead of find-last
@ -82,14 +79,36 @@ C: <combination> combination
x v b nCk - ! x'
v ; ! v == a'
: initial-values ( combination m -- a b x )
[ [ n>> ] [ k>> ] [ ] tri ] dip dual-index ;
: dual-index ( combo m -- x )
[ [ seq>> length ] [ k>> ] bi nCk 1 - ] dip - ;
: combinadic ( combination m -- combinadic )
: initial-values ( combo m -- a b x )
[ [ seq>> length ] [ k>> ] [ ] tri ] dip dual-index ;
: combinadic ( combo m -- combinadic )
initial-values [ over 0 > ] [ next-values ] produce
[ 3drop ] dip ;
: combination-indices ( m combo -- seq )
[ swap combinadic ] keep
seq>> length 1 - swap [ - ] with map ;
: apply-combination ( m combo -- seq )
[ combination-indices ] keep seq>> nths ;
: choose ( combo -- nCk )
[ seq>> length ] [ k>> ] bi nCk ;
PRIVATE>
: combination ( m combination -- seq )
swap [ drop n>> 1 - ] [ combinadic ] 2bi [ - ] with map ;
: combination ( m seq k -- seq )
<combo> apply-combination ;
: all-combinations ( seq k -- seq )
<combo> [ choose [0,b) ] keep
'[ _ apply-combination ] map ;
: each-combination ( seq k quot -- )
[ <combo> [ choose [0,b) ] keep ] dip
'[ _ apply-combination @ ] each ; inline