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Re: combinations

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s" abcde" 2constant test

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: cellbits ( n -- n1 )
	0 swap begin dup 0<> while dup 1 and if >r 1+ r> then 2/ repeat drop ;

( a - number of members in the set )
( b - how many to pick at a time )
: chooseinit ( a b -- m n m )
	dup 0> >r over over > >r over 32 < r> r> and and if >r 1 swap lshift r> over else abort then ;

: choose ( m n a -- m n a' f )
	dup 0= if FALSE else 1- 2dup cellbits = if TRUE else FALSE then then ;
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: str>member ( string n -- )
	." (" begin dup 0> while
		dup 1 and if >r 2dup + 1- c@ emit ."  " r> then
		2/ swap 1- swap
		repeat drop 2drop ." )" ;

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: start ( -- )
	cr
	TEST NIP ( len ) 3 CHOOSEINIT
	BEGIN	DUP 0> WHILE
	CHOOSE IF dup test rot str>member cr THEN
	REPEAT DROP DROP DROP
	; start
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\ To use call chooseinit first then choose.
\ for example to say '5 choose 3' load test$ with 5 unique members.
\ call 5 3 chooseinit which sets up the parameters for choose on the stack
\ call choose which returns a flag, you know you are done when count goes to
\ zero. if choose returns true then number is part of your set &
\ false means ignore number.
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Re: combinations november.nihal@gmail.com - 2013-08-08 03:24 -0700
  Re: combinations Coos Haak <chforth@hccnet.nl> - 2013-08-09 02:44 +0200

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