line-points ( pt1 pt2 -- points )

Vocabulary

rosetta-code.bitmap-line

Inputs

pt1	an object
pt2	an object

Outputs

points

an object

Definition

USING: arrays kernel math ranges sequences ;

IN: rosetta-code.bitmap-line

:: line-points ( pt1 pt2 -- points )
    pt1 first2 :> y0! :> x0! pt2 first2 :> y1! :> x1! y1 y0 -
    abs x1 x0 - abs > :> steep steep
    [ y0 x0 y0! x0! y1 x1 y1! x1! ] when x0 x1 >
    [ x0 x1 x0! x1! y0 y1 y0! y1! ] when x1 x0 -
    :> deltax y1 y0 -
    abs :> deltay 0 :> current-error! deltay deltax /
    abs :> deltaerr 0 :> ystep! y0 :> y! y0 y1 <
    [ 1 ystep! ] [ -1 ystep! ] if x0 x1 1 <range> [
        y steep [ swap ] when 2array current-error deltaerr +
        current-error! current-error 0.5 >=
        [ ystep y + y! current-error 1 - current-error! ] when
    ] { } map-as ;