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I wanted algebraic effects and handlers. Instead all I got was DI. 🤪
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Effects and handlers allow you to do similar stuff to DI (actually quite similar to aspect-oriented programming). They are pretty much accepted as a given in most PL conferences these days - but still need some stuff to be figured out. So at least we have this nice crate!
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Need good, guaranteed fusion of handlers like iterators enjoy in Rust before they are viable for a Rust-like language. The future is exciting though!
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do you have good examples of this? I have to admit I’m not familiar with effects and handlers, although I’ve noticed recently more and more haskell devs talk about effects
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I'll see if I can dig some up. As horrific as this sounds, think: "generalised exception handling". Effects are treated as things that you 'throw' and are handled somewhere else, potentially throwing new effects. All tracked in the type system.
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So I could define a 'Log' effect with a constructor 'trace'. Then my application code could potentially do logging, but it's up to the top level caller of the application to do something with those thrown effects, potentially logging to standard out, or a file.
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Similar to the condition system in the Common Lisp and Dylan languages.
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Oh, haha, Rust used to have a condition system 😂
The punchline to this sad story is that there’s already enough machinery to express the fast & ubiquitous cases via implicits, and rust has no more (cognitive) room in its static type system for more degrees of polymorphism to handle the exceptional cases.
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And if you only do it dynamically everyone just yells “zero cost” until you take it out.
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