Trying out different ways to avoid toFloat conversions, based on this discussion (https://groups.google.com/forum/#!topic/elm-discuss/YPA2ww2P9PU)

Floatify.elm

import Window
import Color

floatify : (Int,Int) -> (Float,Float)
floatify (x,y) =
  (toFloat x, toFloat y)

scene (w,h) =
  flow down
    [ container (floor w) (floor (h / 2)) middle (asText "blue")
        |> color Color.blue
    , container (floor w) (ceiling (h / 2)) middle (asText "red")
        |> color Color.red
    ]

main = lift scene (lift floatify Window.dimensions)

Original-Better.elm

import Window
import Color

scene (w,h) =
  let halfHeight = h // 2
  flow down
    [ container w halfHeight middle (asText "blue")
        |> color Color.blue
    , container w (h - halfHeight) middle (asText "red")
        |> color Color.red
    ]

main = lift scene Window.dimensions

Original-Minimal.elm

import Window
import Color

scene (w,h) =
  flow down
    [ container w (floor (toFloat h / 2)) middle (asText "blue")
        |> color Color.blue
    , container w (ceiling (toFloat h / 2)) middle (asText "red")
        |> color Color.red
    ]

main = lift scene Window.dimensions

Original.elm

import Window
import Color

scene (w,h) = flow down
  [ container w (toFloat h/toFloat 2 |> floor) middle (asText "blue") |> color Color.blue
  , container w (toFloat h/toFloat 2 |> ceiling) middle (asText "red") |> color Color.red
  ]

main = lift scene Window.dimensions