ppop ( seq -- seq' ) - Factor Documentation

ppop ( seq -- seq' )
Persistent sequence protocol

Prev: ppush ( val seq -- seq' )

Vocabulary
persistent .sequences

Inputs

seq a sequence

Outputs

seq' a sequence

Generic word contract
Persistent analogue of pop* . Outputs a new sequence with all elements of seq except for the final element.

Definition

IN: persistent.sequences

GENERIC: ppop ( seq -- seq' )

Methods

USING: accessors combinators kernel math persistent.sequences
persistent.vectors persistent.vectors.private sequences ;

M: persistent-vector ppop
dup count>> {
{ 0 [ empty-error ] }
{ 1 [ drop PV{ } ] }
[
[
clone dup tail>> children>> length 1 >
[ ppop-tail ] [ ppop-new-tail ] if
] dip 1 - >>count
]
} case ;

USING: persistent.sequences sequences ;

M: sequence ppop but-last ;

USING: accessors kernel math persistent.sequences sequences
vlists ;

M: vlist ppop
[ empty-vlist-error ]
[ [ length>> 1 - ] [ vector>> ] bi vlist boa ] if-empty ;