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lazy-lists: fix laziness of lappend 

lappend would evaluate the car of the second list all the time
darcs
chris.double 2006-10-06 03:29:50 +00:00
parent 8586c82066
commit b66cee04b3
1 changed files with 2 additions and 4 deletions
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6
contrib/lazy-lists/lists.factor
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@ -281,9 +281,7 @@ TUPLE: lazy-append list1 list2 ;
: lappend ( list1 list2 -- result ) : lappend ( list1 list2 -- result )
{ {
{ [ over nil? over nil? and ] [ 2drop nil ] }
{ [ over nil? ] [ nip ] } { [ over nil? ] [ nip ] }
{ [ dup nil? ] [ drop ] }
{ [ t ] [ <lazy-append> ] } { [ t ] [ <lazy-append> ] }
} cond ; } cond ;
@ -296,9 +294,9 @@ M: lazy-append cdr ( lazy-append -- cdr )
M: lazy-append nil? ( lazy-append -- bool ) M: lazy-append nil? ( lazy-append -- bool )
dup lazy-append-list1 nil? [ dup lazy-append-list1 nil? [
drop t
] [
lazy-append-list2 nil? lazy-append-list2 nil?
] [
drop f
] if ; ] if ;
M: lazy-append list? ( object -- bool ) M: lazy-append list? ( object -- bool )