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31 lines
1.1 KiB
Haskell
31 lines
1.1 KiB
Haskell
{-# OPTIONS_GHC -fglasgow-exts #-}
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module GFCC.ComposOp (Compos(..),composOp,composOpM,composOpM_,composOpMonoid,
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composOpMPlus,composOpFold) where
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import Control.Monad.Identity
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import Data.Monoid
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class Compos t where
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compos :: (forall a. a -> m a) -> (forall a b. m (a -> b) -> m a -> m b)
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-> (forall a. t a -> m (t a)) -> t c -> m (t c)
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composOp :: Compos t => (forall a. t a -> t a) -> t c -> t c
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composOp f = runIdentity . composOpM (Identity . f)
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composOpM :: (Compos t, Monad m) => (forall a. t a -> m (t a)) -> t c -> m (t c)
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composOpM = compos return ap
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composOpM_ :: (Compos t, Monad m) => (forall a. t a -> m ()) -> t c -> m ()
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composOpM_ = composOpFold (return ()) (>>)
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composOpMonoid :: (Compos t, Monoid m) => (forall a. t a -> m) -> t c -> m
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composOpMonoid = composOpFold mempty mappend
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composOpMPlus :: (Compos t, MonadPlus m) => (forall a. t a -> m b) -> t c -> m b
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composOpMPlus = composOpFold mzero mplus
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composOpFold :: Compos t => b -> (b -> b -> b) -> (forall a. t a -> b) -> t c -> b
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composOpFold z c f = unC . compos (\_ -> C z) (\(C x) (C y) -> C (c x y)) (C . f)
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newtype C b a = C { unC :: b }
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