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{-# OPTIONS -XRebindableSyntax #-}
-- This one tests rebindable syntax for do-notation
module Main where
import qualified Prelude
import GHC.Num
import GHC.Base hiding( Monad(..) )
class Foo a where
op :: a -> a
data T a = MkT a
instance Foo Int where
op x = x+1
(>>=) :: Foo a => T a -> (a -> T b) -> T b
(>>=) (MkT x) f = f (op x)
(>>) :: Foo a => T a -> T b -> T b
(>>) x y = x >>= (\_ -> y)
return :: Num a => a -> T a
return x = MkT (x+1)
fail :: String -> T a
fail s = error "urk"
t1 :: T Int
t1 = MkT 4
myt = do { x <- t1
; return x }
main = case myt of
MkT i -> Prelude.print i
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