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24 lines
737 B
Idris
24 lines
737 B
Idris
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module Bimonad
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import Biapplicative
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infixl 4 >>==
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||| Bimonads
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||| @p the action of the first Bifunctor component on pairs of objects
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||| @q the action of the second Bifunctor component on pairs of objects
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interface (Biapplicative p, Biapplicative q) =>
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Bimonad (p : Type -> Type -> Type) (q : Type -> Type -> Type) where
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bijoin : (p (p a b) (q a b), q (p a b) (q a b)) -> (p a b, q a b)
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bijoin p = p >>== (id, id)
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(>>==) : (p a b, q a b) -> ((a -> p c d), (b -> q c d)) -> (p c d, q c d)
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(pab, qab) >>== (f, g) = bijoin $ (bimap f g, bimap f g) <<*>> (pab, qab)
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biunit : (Bimonad p q) => a -> b -> (p a b, q a b)
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biunit a b = (bipure a b, bipure a b)
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implementation Bimonad Pair Pair where
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bijoin = bimap fst snd
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