Possible runtime overhead of wrapping the IO monad?

[Brian Hulley]

Apologies for the syntax/type errors in my last post! :-)

Brian Hulley wrote:
>       type RenderCallback :: IO ()
>       type KeypressCallback :: IO ()

type RenderCallback = IO ()
type KeypressCallback = Int -> IO ()

>        keypress :: IO ()
>        keypress = drawPrimitive -- not allowed at this point!!!

keypress :: KeypressCallback
keypress c = drawPrimitive -- not allowed at this point!!