new-nth ( val i seq -- seq' )
Persistent sequence protocol

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ppush ( val seq -- seq' )

Vocabulary
persistent.sequences

Inputs

val	an object
i	an integer
seq	a sequence

Outputs

seq'	a sequence

Generic word contract
Persistent analogue of set-nth. Outputs a new sequence with the ith element replaced by val.

Definition

IN: persistent.sequences

GENERIC: new-nth ( val i seq -- seq' )

Methods

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

M: persistent-vector new-nth
    2dup count>> =
    [ nip ppush ] [
        clone 2dup tail-offset >=
        [ [ node-mask ] dip [ node-set-nth ] change-tail ]
        [ [ (new-nth) ] change-root ] if
    ] if ;


USING: kernel persistent.sequences sequences ;

M: sequence new-nth clone [ set-nth ] keep ;