recursionschemes
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335  338  
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4.9  3.6  
3 days ago  7 months ago  
Haskell  Haskell  
BSD 2clause "Simplified" License  BSD 3clause "New" or "Revised" License 
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recursionschemes

❄️ 2023 Day 4 Solutions ❄️
Reasonably proud of my part 2 solution, although would like to try using a recursion scheme rather than unstructured recursion:

Interactive animations
Yeah, that project is pretty much at the bottom of my list, unfortunately. My top projects these days are mgmt, klister, recursionschemes, and hint... And that's already too much!

Science of Recursion
In a programming context, recursion schemes can be used to write recursive (or corecursive) functions, by automating/abstracting away the common boilerplate part of actually doing the recursion. They take the form of polymorphic higherorder functions, which can be imported from a library like this classic one.

Is there a way to avoid call overhead?
Maybe I didn't link the best post. It is unfortunately the only one I know that uses Rust. If you are able to read Haskell, the documentation for the recursionschemes package might be a better resource?

Ah yes I love arrays with a length of infinity!!!
Writing something as a type of fold over an infinite sequence is nicer than using recursion directly in my opinion. See: https://hackage.haskell.org/package/recursionschemes

Tips on mastering recursion and trees and shit?
Consider recursion schemes! It let's you separate the logic of how your recursion is structured on your data, and the logic of what you're doing on each recursion stage. So e.g. you can write the core logic of a recursive linked list summation as just fun x accum > x + accum, and then you just find the appropriate recursion scheme to pipe the list values into x and handle recursing to build accum (a catamorphism in this case)

So you come across an undocumented library…
It's a pretty complicated bug, documented in details at https://github.com/recursionschemes/recursionschemes/issues/50

Beautiful ideas in programming: generators and continuations
It’s also trivial and easy in Haskell — you just need an instance of `Foldable` or `Traversable` on your collection, and then you can fold or traverse it in a configurable way. Or for recursive structures, use https://hackage.haskell.org/package/recursionschemes. Or even just pass a traversal function as an argument for maximum flexibility.

fromMaybe is Just a fold
https://hackage.haskell.org/package/recursionschemes is the "normal" library for this type of generalized folding. It even contains Base instances for Maybe and Either.

Annotation via anamorphism?
I've been working on a system which uses recursionschemes to annotate a recursive type. The annotated tree itself is pretty simple; at each level, we pair the annotation with the base functor, or
machines
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Tracking mentions began in Dec 2020.
What are some alternatives?
distributedprocessplatform  DEPRECATED (Cloud Haskell Platform) in favor of distributedprocessextras, distributedprocessasync, distributedprocessclientserver, distributedprocessregistry, distributedprocesssupervisor, distributedprocesstask and distributedprocessexecution
pipes  Compositional pipelines
record  Anonymous records
daemons  Daemons in Haskell made fun and easy
unliftio  The MonadUnliftIO typeclass for unlifting monads to IO
staticclosure
pipescore  Compositional pipelines
capability  Extensional capabilities and deriving combinators
chrcore  Constraint Handling Rules
fusedeffects  A fast, flexible, fused effect system for Haskell
freersimple  A friendly effect system for Haskell
extensibleeffects  Extensible Effects: An Alternative to Monad Transformers