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The CL condition system always gets brought up when people unfamiliar with effects see effects for the first time (example: https://news.ycombinator.com/item?id=38813484, another example: https://lobste.rs/s/12m2f0/algebraic_effects_another_mistake).

But while the condition system can do many things you can also do with effects, they cannot do everything.

Here's another discussion on this: https://news.ycombinator.com/item?id=44078743

CL conditions do what you actually need if you program. CL gives you deterministic state, safe resource management etc.

Nondeterminism is not a feature you want. Algebraic effects treat the execution stack (continuation) as data, you have total freedom over what you do with it. This flexibility is exactly where you get nondeterminism. This is how logic solvers or probabilistic algorithms work, but you don't want it as a programming language feature in general purpose programming language.

It’s pretty annoying to comment “this thing was already present in CL 30 years ago”, then to have someone correct you (pointing out that this is a common misconception, and algebraic effects are not equivalent to conditions at all), and then to respond not to admit you’re wrong but instead to say “algebraic effects are bad anyway because you shouldn’t want one of the extra features they give you (nondeterminism)”.

By the way, nondeterminism is not the only difference between the two.

Standard usable feature. Features must work with everything else in the language.

I like programming language theory as much as anyone else, but there is a reason some language features exist only so that people can blog and think about them.

> Nondeterminism is not a feature you want.

I can get behind the sentiment, but you absolutely need nondeterminism. You can separate the d from the non-d, but only Haskellish languages even attempt it. It's a coarse separation to make (IO vs non-IO), which is where effect systems come in - I guess you can categorise code into more fine-grain buckets. The 'algebraic' part is currently beyond my knowledge.