Hash Codes, Non-Determinism, and Other Eldritch Horrors

Re:Hash Codes, Non-Determinism, and Other Eldritch Horrors by tracnar on Thursday November 10, 2022 @06:33PM (#33555209)

I wonder if a type system could track nondeterminism and prevent it. E.g. you couldn't just loop over a set, you'd have to order it, or apply a commutative operation. It would fit well into concurrency too, where nondeterminism is easily introduced.

I'm sure there are languages which do this, I seem to recall seeing it in Mercury

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Re:Hash Codes, Non-Determinism, and Other Eldritch Horrors by phlip9 on Thursday November 10, 2022 @07:04PM (#33555541)

Languages with first class effects, like koka[1], require you to declare up-front what side effects (sample randomness, do I/O, abort, etc...) your function might cause.

Then from another outer function, you can't call the effectful function unless the outer function also declares those same side-effects (or you provide handlers for them).

This way you can easily isolate non-determinism and I/O to the top-level part of your program, while keeping the interior business logic pure.

The "first-class effects" part is what lets you easily compose effects and inject custom handlers. Ideally in a way that's more ergonomic than juggling with Monad type system Jenga.

[1]: https://koka-lang.github.io/koka/doc/index.html

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