Difference between revisions of "Zygohistomorphic prepromorphisms"
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| − | Zygohistomorphic prepromorphisms are monad transformers that started as a joke the #Haskell IRC channel<ref>[https://archive.ph/2Jlo6] Edward Kmett on Twitter, 2019</ref>. |
+ | Zygohistomorphic prepromorphisms are recursion schemes based on monad transformers that started as a joke the #Haskell IRC channel<ref>[https://archive.ph/2Jlo6] Edward Kmett on Twitter, 2019</ref>. |
Used when you really need both semi-mutual recursion and history and to repeatedly apply a natural transformation as you get deeper into the functor. <code>Zygo</code> implements semi-mutual recursion like a zygomorphism. ''Para'' gives you access to your result à la paramorphism. |
Used when you really need both semi-mutual recursion and history and to repeatedly apply a natural transformation as you get deeper into the functor. <code>Zygo</code> implements semi-mutual recursion like a zygomorphism. ''Para'' gives you access to your result à la paramorphism. |
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Revision as of 15:33, 20 July 2023
Zygohistomorphic prepromorphisms are recursion schemes based on monad transformers that started as a joke the #Haskell IRC channel[1].
Used when you really need both semi-mutual recursion and history and to repeatedly apply a natural transformation as you get deeper into the functor. Zygo implements semi-mutual recursion like a zygomorphism. Para gives you access to your result à la paramorphism.
import Control.Morphism.Zygo
import Control.Morphism.Prepro
import Control.Morphism.Histo
import Control.Functor.Algebra
import Control.Functor.Extras
zygoHistoPrepro
:: (Unfoldable t, Foldable t)
=> (Base t b -> b)
-> (forall c. Base t c -> Base t c)
-> (Base t (EnvT b (Stream (Base t)) a) -> a)
-> t
-> a
zygoHistoPrepro f g t = gprepro (distZygoT f distHisto) g t
-- unless you want a generalized zygomorphism.