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25 lines
756 B
Haskell
25 lines
756 B
Haskell
--- src/Cryptol/Utils/Patterns.hs.orig 2001-09-09 01:46:40 UTC
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+++ src/Cryptol/Utils/Patterns.hs
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@@ -5,6 +5,7 @@
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module Cryptol.Utils.Patterns where
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import Control.Monad(liftM,liftM2,ap,MonadPlus(..),guard)
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+import qualified Control.Monad.Fail as Fail
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import Control.Applicative(Alternative(..))
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newtype Match b = Match (forall r. r -> (b -> r) -> r)
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@@ -17,10 +18,12 @@ instance Applicative Match where
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(<*>) = ap
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instance Monad Match where
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- fail _ = empty
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Match m >>= f = Match $ \no yes -> m no $ \a ->
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let Match n = f a in
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n no yes
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+
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+instance Fail.MonadFail Match where
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+ fail _ = empty
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instance Alternative Match where
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empty = Match $ \no _ -> no
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