lfilter ( list quot: ( elt -- ? ) -- result )
Lazy lists » Combinators for manipulating lazy lists

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Vocabulary
lists.lazy

Inputs

list	a cons object
quot	a quotation with stack effect ( elt -- ? )

Outputs

result

resulting cons object

Word description
Perform a similar functionality to that of the filter word, but in a lazy manner. No evaluation of the list elements occurs initially but a lazy-filter object is returned which conforms to the list protocol. Calling car, cdr or nil? on this will evaluate elements as required.

Examples

USING: kernel lists lists.lazy math prettyprint ; 1 lfrom [ even? ] lfilter 5 ltake list>array .
{ 2 4 6 8 10 }

See also
leach, foldl, lmap-lazy, ltake, lappend-lazy, lfrom, lfrom-by, lconcat, lcartesian-product, lcartesian-product*, lcartesian-map, lcartesian-map*, lmerge, lwhile, luntil

Definition

USING: kernel lists ;

IN: lists.lazy

: lfilter ( list quot: ( elt -- ? ) -- result )
    over nil? [ 2drop nil ] [ <lazy-filter> <memoized-cons> ] if
    ;