25 lines
981 B
Diff
25 lines
981 B
Diff
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diff --git a/templates/wrappers.hs b/templates/wrappers.hs
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index a1a1a6d..c020cc7 100644
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--- a/templates/wrappers.hs
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+++ b/templates/wrappers.hs
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@@ -284,6 +284,19 @@ runAlex input (Alex f)
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newtype Alex a = Alex { unAlex :: AlexState -> Either String (AlexState, a) }
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+instance Functor Alex where
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+ fmap f a = Alex $ \s -> case unAlex a s of
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+ Left msg -> Left msg
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+ Right (s', a') -> Right (s', f a')
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+
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+instance Applicative Alex where
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+ pure a = Alex $ \s -> Right (s, a)
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+ fa <*> a = Alex $ \s -> case unAlex fa s of
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+ Left msg -> Left msg
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+ Right (s', f) -> case unAlex a s' of
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+ Left msg -> Left msg
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+ Right (s'', b) -> Right (s'', f b)
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+
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instance Monad Alex where
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m >>= k = Alex $ \s -> case unAlex m s of
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Left msg -> Left msg
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