lwhile ( 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
Outputs a lazy list containing the first items in the list as long as quot evaluates to t. No evaluation of the list elements occurs initially but a lazy-while object is returned with 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 [ 5 <= ] lwhile list>array .
{ 1 2 3 4 5 }

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

Definition

USING: kernel lists ;

IN: lists.lazy

: lwhile ( list quot: ( elt -- ? ) -- result )
    over nil? [ drop ] [ <lazy-while> ] if ;