41 lines
891 B
Haskell
41 lines
891 B
Haskell
module MonadHelp
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( module Control.Monad
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, module MonadHelp
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) where
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import Control.Monad
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untilJust :: Monad m => m (Maybe a) -> m a
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untilJust m = go
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where
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go = do
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mayx <- m
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maybe go return mayx
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untilJustCount :: Monad m => m (Maybe a) -> m (a, Int)
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untilJustCount m = go 0
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where
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go i = do
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mayx <- m
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case mayx of
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Nothing -> go (i+1)
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Just x -> return (x,i)
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iterateUntil :: Monad m => (a -> Bool) -> m a -> m a
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iterateUntil t m = do
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x <- m
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if t x
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then return x
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else iterateUntil t m
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iterateWhile :: Monad m => (a -> Bool) -> m a -> m a
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iterateWhile t = iterateUntil (not . t)
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unfoldrMID :: (Monad m) => (a -> m (Maybe a)) -> a -> m [a]
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unfoldrMID f = go
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where
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go z = do
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x <- f z
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case x of
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Nothing -> return [z]
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Just y -> (z :) <$> go y
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