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module Ext () where
-- There were typos in these definitions in the ICFP 2004 paper.
import Data.Generics
extQ fn spec_fn arg
= case gcast (Q spec_fn) of
Just (Q spec_fn') -> spec_fn' arg
Nothing -> fn arg
newtype Q r a = Q (a -> r)
extT fn spec_fn arg
= case gcast (T spec_fn) of
Just (T spec_fn') -> spec_fn' arg
Nothing -> fn arg
newtype T a = T (a -> a)
extM :: (Typeable a, Typeable b)
=> (a -> m a) -> (b -> m b) -> (a -> m a)
extM fn spec_fn
= case gcast (M spec_fn) of
Just (M spec_fn') -> spec_fn'
Nothing -> fn
newtype M m a = M (a -> m a)
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