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{-# LANGUAGE RebindableSyntax #-}
-- Trac #303
module T where
import qualified Prelude as P
class IxMonad m where
return :: a -> m i i a
(>>=) :: m i j a -> (a -> m j k b) -> m i k b
(>>) :: m i j a -> m j k b -> m i k b
m >> n = m >>= \_ -> n
fail :: P.String -> m i j a
fail s = P.error s
data T a b c = T
instance IxMonad T where
return _ = T
m >>= f = T
fail _ = T
testM :: T (a,b) b a
testM = T
test1 = testM >>= \x -> return x
test2 = do
x <- testM
return x
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