bensenhamLine-1.elm

type BrensemhamStatics = Statics (Int, Int) (Float, Float) Coordinate

bresenhamLine : Coordinate -> Coordinate -> List Coordinate
bresenhamLine (x0, y0) (x1, y1) =
  let
    dx = (toFloat << abs) (x1 - x0)
    sx = if x0 < x1 then 1 else -1
    dy = (toFloat << abs) (y1 - y0)
    sy = if y0 < y1 then 1 else -1

    error =
      (if dx > dy then dx else -dy) / 2

    bresenhamLineRecursion = 
      Statics (sx, sy) (dx, dy) (x1, y1)
      |>bresenhamLineLoop
  in
  bresenhamLineRecursion error (x0, y0) []

bresenhamLineLoop : BrensemhamStatics -> Float -> Coordinate -> List Coordinate -> List Coordinate
bresenhamLineLoop statics error (x0, y0) coordinates =
  case statics of
    Statics (sx, sy) (dx, dy) (x1, y1) ->
      let coordinates_ = (x0, y0) :: coordinates in
      if (x0 == x1) && (y0 == y1) then 
        coordinates_
      else
        let
          (dErrX, x0_) =
            if error > -dx then (-dy, sx + x0)
            else (0, x0)

          (dErrY, y0_) =
            if error < dy then (dx, sy + y0)
            else (0, y0)

          error_ = error + dErrX + dErrY
        in
        bresenhamLineLoop statics error_ (x0_, y0_) coordinates_