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rename nths to switches 

add ?nth* and nths to sequences.lib
db4
Doug Coleman 2008-03-06 17:10:56 -06:00
parent 635749a50b
commit 61c77e616f
1 changed files with 9 additions and 3 deletions
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12
extra/sequences/lib/lib.factor
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@ -140,13 +140,13 @@ PRIVATE>
: strings ( alphabet length -- seqs ) : strings ( alphabet length -- seqs )
>r dup length r> number-strings map-alphabet ; >r dup length r> number-strings map-alphabet ;
: nths ( nths seq -- subseq ) : switches ( seq1 seq -- subseq )
! nths is a sequence of ones and zeroes ! seq1 is a sequence of ones and zeroes
>r [ length ] keep [ nth 1 = ] curry subset r> >r [ length ] keep [ nth 1 = ] curry subset r>
[ nth ] curry { } map-as ; [ nth ] curry { } map-as ;
: power-set ( seq -- subsets ) : power-set ( seq -- subsets )
2 over length exact-number-strings swap [ nths ] curry map ; 2 over length exact-number-strings swap [ switches ] curry map ;
: push-either ( elt quot accum1 accum2 -- ) : push-either ( elt quot accum1 accum2 -- )
>r >r keep swap r> r> ? push ; inline >r >r keep swap r> r> ? push ; inline
@ -214,3 +214,9 @@ PRIVATE>
: attempt-each ( seq quot -- result ) : attempt-each ( seq quot -- result )
(each) iterate-prep (attempt-each-integer) ; inline (each) iterate-prep (attempt-each-integer) ; inline
: ?nth* ( n seq -- elt/f ? )
2dup bounds-check? [ nth-unsafe t ] [ 2drop f f ] if ; flushable
: nths ( indices seq -- seq' )
[ swap nth ] with map ;