If I run ghc on
--------------------------------------------------------------------------------
> module Main (main) where
> data ERR a b = EOK a | ERR b deriving (Show)
> data Error = No | Notatall deriving (Show, Eq)
> class MonadErr m e | m -> e where
> aerturn :: e -> m a
> areturn :: a -> m a
> acatch :: a -> (a -> m b) -> (e -> m b) -> m b
> (>>>=) :: m a -> (a -> m b) -> m b
> (>>>) :: m a -> m b -> m b
> data BP a = BP (Int -> (ERR a Error, Int))
> instance MonadErr BP Error where
> aerturn k = BP $ \s -> (ERR k, s)
> areturn k = BP $ \s -> (EOK k, s)
> acatch k try handler = BP $ \s -> let BP try' = try k
> (r,s1) = try' s
> (BP c2, s2) = case r of
> EOK r -> (areturn r, s1)
> ERR r -> (handler r, s)
> in c2 s2
> a >>> b = a >>>= \_ -> b
> (BP c1) >>>= fc2 = BP $ \s0 -> let (r,s1) = c1 s0
> BP c2 = case r of
> EOK r -> fc2 r
> ERR r -> BP (\s -> (ERR r, s))
> in c2 s1
> run_BP :: Int -> BP a -> (ERR a Error, Int)
> run_BP st (BP bp) = bp st
> foo :: (ERR Int Error, Int)
> foo = run_BP 111 (aerturn No)
> main = print (show foo)
--------------------------------------------------------------------------------
I get
ghc -fglasgow-exts Er.lhs -o Er
zonkIdOcc: FunDep_a11w
zonkIdOcc: FunDep_a11t
zonkIdOcc: FunDep_a11t
ghc --version
The Glorious Glasgow Haskell Compilation System, version 4.08.1
What is this about? Is it dangerous? (I.e. will it break my executable?)
Sengan
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