Draw Grid

grid.elm

import Color exposing (..)
import Graphics.Collage exposing (..)
import Graphics.Element exposing (..)
import Window
  
main : Signal Element
main =
  Signal.map render Window.dimensions

renderGridLine : Int -> Int -> Int -> Int -> Form
renderGridLine ax ay bx by =
  traced (dashed red) (path ([(toFloat ax, toFloat ay), (toFloat bx, toFloat by)]))

renderGridLines : Int -> Int -> Int -> (Int -> Int -> Form) -> List Form
renderGridLines gridsz cellsz i renderLine =
  if i == 0 then [] else
    let j = i - 1
        pos = j * cellsz 
    in (renderLine pos gridsz) :: (renderGridLines gridsz cellsz j renderLine)

renderGrid : Int -> Int -> Int -> Int -> Element
renderGrid gridsz cellsz gx gy =
  let renderHor = \pos sz -> renderGridLine pos 0 pos sz 
      renderVer = \pos sz -> renderGridLine 0 pos sz pos
      grid = (renderGridLines gridsz cellsz gy renderHor) ++
        (renderGridLines gridsz cellsz gx renderVer)
  in
    collage gridsz gridsz grid

render : (Int, Int) -> Element
render (x, y) =
  renderGrid 400 50 8 8