#1 Handle multiple key input

lib/InputHandler.hs

@@ -0,0 +1,60 @@
+module InputHandler 
+( Event
+
+, handleInput
+, composeInputHandler
+
+, handleSpace
+, handleEnter
+, handleUp
+, handleDown
+, handleLeft
+, handleRight
+) where
+
+import Graphics.Gloss
+import qualified Graphics.Gloss.Interface.IO.Game as Game
+
+----------------------------- Constants ------------------------------
+
+-- Something that happens, most often a keypress
+type Event = Game.Event
+
+----------------------------------------------------------------------
+
+-- Handle input by taking a keyCheck function that checks wheter or not
+-- a key is being presse
+handleInput :: Game.SpecialKey -> (a -> a) -> Event -> a -> a
+handleInput key convert ev currentState
+    | isKey key ev = convert currentState
+    | otherwise    = currentState
+
+-- Compose multiple InputHandlers into one combined InputHandler.
+composeInputHandler :: [Event -> a -> a] -> Event -> a -> a
+composeInputHandler (ih:ihs) ev a = composeInputHandler ihs ev (ih ev a)
+composeInputHandler []       ev a = a
+
+-- Check if the requested key is pressed.
+isKey :: Game.SpecialKey -> Event -> Bool
+isKey k1 (Game.EventKey (Game.SpecialKey k2) Game.Down _ _) = k1 == k2
+isKey _  _                                                  = False
+
+------------------ A couple of default inputhandlers -----------------
+
+handleSpace :: (a -> a) -> Event -> a -> a
+handleSpace = handleInput Game.KeySpace
+
+handleEnter :: (a -> a) -> Event -> a -> a
+handleEnter = handleInput Game.KeyEnter
+
+handleUp :: (a -> a) -> Event -> a -> a
+handleUp = handleInput Game.KeyUp
+
+handleDown :: (a -> a) -> Event -> a -> a
+handleDown = handleInput Game.KeyDown
+
+handleLeft :: (a -> a) -> Event -> a -> a
+handleLeft = handleInput Game.KeyLeft
+
+handleRight :: (a -> a) -> Event -> a -> a
+handleRight = handleInput Game.KeyRight