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21 lines
481 B
Plaintext
21 lines
481 B
Plaintext
type Cofree f a = Cofree a (f (Cofree f a))
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type Functor f = Functor (forall a b. (a ->{} b) -> f a ->{} f b)
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use Functor Functor
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fmap : Functor f -> (a -> b) -> f a -> f b
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fmap fn f = match fn with
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Functor map -> map f
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use Cofree Cofree
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namespace Cofree where
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extract : Cofree f a -> a
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extract = cases
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Cofree a _ -> a
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duplicate : Functor f -> Cofree f a -> Cofree f (Cofree f a)
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duplicate f c = match c with
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Cofree a p -> Cofree c (fmap f (duplicate f) p)
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