subseq-starts-at? ( i seq subseq -- ? )
Factor handbook » The language » Collections » Sequence operations » Searching sequences

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Vocabulary
sequences

Inputs

i	a start index
seq	a sequence
subseq	a sequence

Outputs

?

a boolean

Word description
Outputs t if the subseq starts at the ith element or outputs f if the sequence is not at that position.

Definition

USING: kernel math sequences.private ;

IN: sequences

: subseq-starts-at? ( i seq subseq -- ? )
    [ length swap ] keep
    [ [ [ + ] ] dip [ nth-unsafe ] curry compose ] dip
    [ [ keep ] curry ] dip [ nth-unsafe = ] curry compose with
    all-integers? ; inline