elm add

gistfile1.txt

import String
import Graphics.Input (Input, input)
import Graphics.Input.Field as Field

lhd : Input Field.Content
lhd = input Field.noContent

rhd : Input Field.Content
rhd = input Field.noContent

main : Signal Element
main = lift2 scene lhd.signal rhd.signal

scene : Field.Content -> Field.Content -> Element
scene lContent rContent =
  flow right
    (map (\x -> (container 50 50 middle (width 50 x)))
      [
        Field.field Field.defaultStyle lhd.handle identity "" lContent
      , plainText ("+")
      , Field.field Field.defaultStyle rhd.handle identity "" rContent
      , plainText ("=")
      , plainText (add (String.toInt lContent.string) (String.toInt rContent.string))
    ])  

add : Maybe Int-> Maybe Int -> String
add xstr ystr =
  case xstr of
    Nothing -> "err"
    Just x ->
      case ystr of
        Nothing -> "err"
        Just y -> String.show (x + y)