count-neighbors ( grid -- counts )

Vocabulary

game-of-life

Inputs

grid

an object

Outputs

counts

an object

Definition

USING: arrays bit-arrays byte-arrays kernel kernel.private math
sequences sequences.private ;

IN: game-of-life

:: count-neighbors ( grid -- counts )
    grid grid-dim { fixnum fixnum } declare
    :> ( rows cols ) rows 1 - { fixnum } declare
    :> max-rows cols 1 - { fixnum } declare :> max-cols rows
    [ cols <byte-array> ] replicate :> neighbors grid
    { array } declare [| row j |
        j 0 eq? [ max-rows ] [ j 1 - ] if j j max-rows eq?
        [ 0 ] [ j 1 + ] if
        [ neighbors nth-unsafe { byte-array } declare ] tri@
        :> ( above same below ) row { bit-array } declare [|
        cell i |
            cell [
                i 0 eq? [ max-cols ] [ i 1 - ] if
                i i max-cols eq? [ 0 ] [ i 1 + ] if
                [ [ above ~quotation~ change-nth-unsafe ] tri@ ] 
                [
                    nip
                    [ same ~quotation~ change-nth-unsafe ] bi@
                ]
                [ [ below ~quotation~ change-nth-unsafe ] tri@ ]
                3tri
            ] when
        ] each-index
    ] each-index neighbors ;