gistfile1.txt

data Maybe a = Nothing | Just a

bind :: Maybe a -> (a -> Maybe b) -> Maybe b
bind m f = case m of 
             Just x  -> f x
             Nothing -> Nothing

return :: a -> Maybe a
return x = Just x

mzero :: Maybe ()
mzero = Just ()

delay :: Thunk (Maybe a) -> Thunk (Maybe a) 
delay f = f 

combine :: Maybe a -> Thunk (Maybe a) -> Maybe a
combine m f = bind m f

run :: Thunk (Maybe a) -> Maybe a
run f = f ()

while :: Thunk Bool -> Thunk (Maybe a) -> Maybe a
while cond f = if cond () then bind f ()  fun _ -> while cond f 
                          else zero()

let maybe = OptionBuilder()