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27 lines
744 B
Haskell
27 lines
744 B
Haskell
module Util.Function where
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import Startlude
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(.*) :: (b -> c) -> (a0 -> a1 -> b) -> a0 -> a1 -> c
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(.*) = (.) . (.)
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(.**) :: (b -> c) -> (a0 -> a1 -> a2 -> b) -> a0 -> a1 -> a2 -> c
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(.**) = (.) . (.*)
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preimage :: Eq b => (a -> b) -> b -> [a] -> [a]
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preimage f target = filter ((== target) . f)
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mapFind :: ([a] -> Maybe a) -> (b -> a) -> [b] -> Maybe b
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mapFind _ _ [] = Nothing
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mapFind finder mapping (b : bs) =
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let mB = mapFind finder mapping bs
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mA = finder [mapping b]
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in case (mB, mA) of
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(Just b', _ ) -> Just b'
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(Nothing, Just _) -> Just b
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_ -> Nothing
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(<<&>>) :: (Functor f, Functor g) => f (g a) -> (a -> b) -> f (g b)
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f <<&>> fab = fmap (fmap fab) f
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