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49 lines
1.2 KiB
Idris
49 lines
1.2 KiB
Idris
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module Data.These
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%default total
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public export
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data These a b = This a | That b | Both a b
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public export
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fromEither : Either a b -> These a b
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fromEither = either This That
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public export
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these : (a -> c) -> (b -> c) -> (a -> b -> c) -> These a b -> c
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these l r lr (This a) = l a
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these l r lr (That b) = r b
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these l r lr (Both a b) = lr a b
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public export
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bimap : (f : a -> b) -> (g : c -> d) -> These a c -> These b d
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bimap f g (This a) = This (f a)
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bimap f g (That b) = That (g b)
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bimap f g (Both a b) = Both (f a) (g b)
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public export
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(Show a, Show b) => Show (These a b) where
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showPrec d (This x) = showCon d "This" $ showArg x
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showPrec d (That x) = showCon d "That" $ showArg x
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showPrec d (Both x y) = showCon d "Both" $ showArg x ++ showArg y
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public export
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Functor (These a) where
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map = bimap id
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public export
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mapFst : (f : a -> b) -> These a c -> These b c
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mapFst f = bimap f id
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public export
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bifold : Monoid m => These m m -> m
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bifold (This a) = a
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bifold (That b) = b
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bifold (Both a b) = a <+> b
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public export
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bitraverse : Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d)
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bitraverse f g (This a) = [| This (f a) |]
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bitraverse f g (That b) = [| That (g b) |]
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bitraverse f g (Both a b) = [| Both (f a) (g b) |]
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