HXQ-0.17.0: src/DeepSeq.hs

{-
stolen from comp.lang.functional from Dean Herington
DeepSeq.lhs -- deep strict evaluation support
The DeepSeq class provides a method deepSeq that is similar to seq
except that it forces deep evaluation of its first argument before
returning its second argument.
Instances of DeepSeq are provided for Prelude types. Other instances
must be supplied by users of this module.
-}


module  DeepSeq  where


class  DeepSeq a  where  deepSeq :: a -> b -> b


infixr 0 `deepSeq`, $!!


($!!) :: (DeepSeq a) => (a -> b) -> a -> b
f $!! x = x `deepSeq` f x


instance  DeepSeq ()  where  deepSeq = seq


instance  DeepSeq Bool  where  deepSeq = seq
instance  DeepSeq Char  where  deepSeq = seq


instance  (DeepSeq a) => DeepSeq (Maybe a)  where
  deepSeq Nothing  y = y
  deepSeq (Just x) y = deepSeq x y


instance  (DeepSeq a, DeepSeq b) => DeepSeq (Either a b)  where
  deepSeq (Left  a) y = deepSeq a y
  deepSeq (Right b) y = deepSeq b y


instance  DeepSeq Ordering  where  deepSeq = seq


instance  DeepSeq Int       where  deepSeq = seq
instance  DeepSeq Integer   where  deepSeq = seq
instance  DeepSeq Float     where  deepSeq = seq
instance  DeepSeq Double    where  deepSeq = seq


instance  DeepSeq (a -> b)  where  deepSeq = seq


instance  DeepSeq (IO a)  where  deepSeq = seq


instance  (DeepSeq a) => DeepSeq [a]  where
  deepSeq []     y = y
  deepSeq (x:xs) y = deepSeq x $ deepSeq xs y


instance  (DeepSeq a,DeepSeq b) => DeepSeq (a,b)  where
  deepSeq (a,b)           y = deepSeq a $ deepSeq b y
instance  (DeepSeq a,DeepSeq b,DeepSeq c) => DeepSeq (a,b,c)  where
  deepSeq (a,b,c)         y = deepSeq a $ deepSeq b $ deepSeq c y
instance  (DeepSeq a,DeepSeq b,DeepSeq c,DeepSeq d) => DeepSeq (a,b,c,d)  where
  deepSeq (a,b,c,d)       y = deepSeq a $ deepSeq b $ deepSeq c $ deepSeq d y
instance  (DeepSeq a,DeepSeq b,DeepSeq c,DeepSeq d,DeepSeq e) => DeepSeq (a,b,c,d,e)  where
  deepSeq (a,b,c,d,e)     y = deepSeq a $ deepSeq b $ deepSeq c $ deepSeq d $ deepSeq e y
instance  (DeepSeq a,DeepSeq b,DeepSeq c,DeepSeq d,DeepSeq e,DeepSeq f) => DeepSeq (a,b,c,d,e,f)  where
  deepSeq (a,b,c,d,e,f)   y = deepSeq a $ deepSeq b $ deepSeq c $ deepSeq d $ deepSeq e $ deepSeq f y
instance  (DeepSeq a,DeepSeq b,DeepSeq c,DeepSeq d,DeepSeq e,DeepSeq f,DeepSeq g) => DeepSeq (a,b,c,d,e,f,g)  where
  deepSeq (a,b,c,d,e,f,g) y = deepSeq a $ deepSeq b $ deepSeq c $ deepSeq d $ deepSeq e $ deepSeq f $ deepSeq g y