find-nth-from ( nth from seq quot: ( obj -- ? ) -- i/f obj/f )

Vocabulary

sequences.extras

Inputs

nth	an object
from	an object
seq	an object
quot	a quotation with stack effect ( obj -- ? )

Outputs

i/f	an object
obj/f	an object

Definition

USING: kernel math sequences shuffle ;

IN: sequences.extras

: find-nth-from
    ( nth from seq quot: ( obj -- ? ) -- i/f obj/f )
    reach 0 <
    [ [ neg 1 - ] 3dip [ 1 - ] 2dip find-nth-last-from ] [
        [ 0 ] 4dip [
            2swap [ call ] 2dip rot
            [ [ 1 + ] dip 2dup > ] [ f ] if
        ] curry find-from 2nipd
    ] if ; inline recursive