nil? ( object -- ? )
Factor handbook » The language » Collections » Lists » The list protocol

Prev:

cdr ( cons -- cdr )

Vocabulary
lists

Inputs

object

an object

Outputs

?

a boolean

Word description
Return true if the cons object is the nil cons.

See also
nil

Definition

IN: lists

GENERIC: nil? ( object -- ? )

Methods

USING: kernel lists ;

M: +nil+ nil? drop t ;


USING: kernel lists lists.lazy ;

M: lazy-append nil? drop f ;


USING: accessors kernel lists lists.lazy ;

M: lazy-concat nil?
    dup car>> nil? [ cdr>> nil? ] [ drop f ] if ;


USING: lists lists.lazy ;

M: lazy-cons-state nil? car nil? ;


USING: accessors combinators kernel lists lists.lazy
lists.lazy.private ;

M: lazy-filter nil?
    {
        { [ dup cons>> nil? ] [ drop t ] }
        { [ dup car-filtered? ] [ drop f ] }
        [ skip nil? ]
    } cond ;


USING: kernel lists lists.lazy ;

M: lazy-from-by nil? drop f ;


USING: lists lists.lazy ;

M: lazy-io nil? car nil? ;


USING: accessors lists lists.lazy ;

M: lazy-map nil? cons>> nil? ;


USING: accessors kernel lists lists.lazy math ;

M: lazy-take nil? dup n>> zero? [ drop t ] [ cons>> nil? ] if ;


USING: kernel lists lists.lazy ;

M: lazy-until nil? drop f ;


USING: accessors combinators kernel lists lists.lazy ;

M: lazy-while nil?
    [ car ] keep quot>> ( elt -- ? ) call-effect not ;


USING: kernel lists lists.lazy ;

M: lazy-zip nil? drop f ;


USING: lazy lists ;

M: lazy nil? force nil? ;


USING: accessors kernel lists lists.lazy ;

M: memoized-cons nil?
    dup nil?>> +not-memoized+ eq?
    [ dup original>> nil? [ >>nil? drop ] keep ] [ nil?>> ] if ;


USING: kernel lists ;

M: object nil? drop f ;


USING: kernel lists lists.lazy ;

M: sequence-cons nil? drop f ;