recursion-schemes
unliftio
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recursion-schemes | unliftio | |
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20 | 5 | |
335 | 150 | |
0.6% | 0.0% | |
4.9 | 3.9 | |
3 days ago | 3 months ago | |
Haskell | Haskell | |
BSD 2-clause "Simplified" License | GNU General Public License v3.0 or later |
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recursion-schemes
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-❄️- 2023 Day 4 Solutions -❄️-
Reasonably proud of my part 2 solution, although would like to try using a recursion scheme rather than unstructured recursion:
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Interactive animations
Yeah, that project is pretty much at the bottom of my list, unfortunately. My top projects these days are mgmt, klister, recursion-schemes, and hint... And that's already too much!
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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 higher-order functions, which can be imported from a library like this classic one.
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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 recursion-schemes package might be a better resource?
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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/recursion-schemes
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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)
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So you come across an undocumented library…
It's a pretty complicated bug, documented in details at https://github.com/recursion-schemes/recursion-schemes/issues/50
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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/recursion-schemes. Or even just pass a traversal function as an argument for maximum flexibility.
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fromMaybe is Just a fold
https://hackage.haskell.org/package/recursion-schemes is the "normal" library for this type of generalized folding. It even contains Base instances for Maybe and Either.
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Annotation via anamorphism?
I've been working on a system which uses recursion-schemes to annotate a recursive type. The annotated tree itself is pretty simple; at each level, we pair the annotation with the base functor, or
unliftio
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UnliftIO, ExceptT and Coercible
FWIW, your suggestion is very similar to a proposed instance for MonadUnliftIO (ExceptT e), except that effectfuls use of the type system means that it doesn't suffer from one of the proposed downsides (dubious interaction with catchAny).
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How introduce `ResourceT` into my stack
Possibly interesting thread here: https://github.com/fpco/unliftio/issues/68
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Is `MonadBaseControl` dead?
Any way quoting u/snoyberg : https://github.com/fpco/unliftio/issues/17#issuecomment-363655106
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Try.do is dangerous
That's not true. It's just writing that instance is a bit tricky: https://github.com/fpco/unliftio/issues/68
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Try.do for recoverable errors in Haskell
However, ExceptT cannot be an instance of MonadUnliftIO – because it necessarily requires multiple exit points. See this discussion which should give you an idea of how hairy and unpredictable this can be.
What are some alternatives?
distributed-process-platform - DEPRECATED (Cloud Haskell Platform) in favor of distributed-process-extras, distributed-process-async, distributed-process-client-server, distributed-process-registry, distributed-process-supervisor, distributed-process-task and distributed-process-execution
lifted-base - IO operations from the base library lifted to any instance of MonadBase or MonadBaseControl
record - Anonymous records
mmorph - Monad morphisms
machines - Networks of composable stream transducers
Workflow - re-startable monad that recover the execution state from a log, and workflow patterns
pipes-core - Compositional pipelines
exceptional - A simple Haskell type for pure code that could go wrong.
chr-core - Constraint Handling Rules
managed - A monad for managed values
freer-simple - A friendly effect system for Haskell
effectful - An easy to use, fast extensible effects library with seamless integration with the existing Haskell ecosystem.