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0 pointssimonask4mo ago0 comments

Comparing type systems is difficult, but the general experience is that it is significantly easier to encode logic invariants in Rust than in C++.

Some of the things you can do, often with a wild amount of boilerplate (tagged unions, niches, etc.), and some of the things are fundamentally impossible (movable non-null owning references).

C++ templates are more powerful than Rust generics, but the available tools in Rust are more sophisticated.

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sunshowers4mo ago

Note that while C++ templates are more powerful than Rust generics at being able to express different patterns of code, Rust generics are better at producing useful error messages. To me, personally, good error messages are the most fundamental part of a compiler frontend.

wakawaka284mo ago

Concepts make it possible to generate very clear (even user-friendly) template errors.

sunshowers4mo ago

True but you lose out on much of the functionality of templates, right? Also you only get errors when instantiating concretely, rather than getting errors within the template definition.

wakawaka284mo ago

No, concepts interoperate with templates. I guess if you consider duck typing to be a feature, then using concepts can put constraints on that, but that is literally the purpose of them and nobody makes you use them.

If you aren't instantiating a template, then it isn't used, so who cares if it has theoretical errors to be figured out later? This behavior is in fact used to decide between alternative template specializations for the same template. Concepts do it better in some ways.

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aw16211074mo ago

> but you lose out on much of the functionality of templates, right?

I don't think so? From my understanding what you can do with concepts isn't much different from what you can do with SFINAE. It (primarily?) just allows for friendlier diagnostics further up in the call chain.

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wakawaka284mo ago

I don't agree that Rust tools are more sophisticated and they definitely are not more abundant. You just have a language that is more anal up front. C++ has many different compilers, analyzers, debuggers, linting tools, leak detectors, profilers, etc. It turns out that 40 years of use leads to significant development that is hard to rebuild from scratch.

I seem to have struck a nerve with my post, which got 4 downvotes so far. Just for saying Rust is not actually better than C++ in this one regard lol.

simonaskOP4mo ago

I think it’s because you misread my comment by skimming over the important parts.

This isn’t about tooling, it’s about language features and type systems.

j / k navigate · click thread line to collapse

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sunshowers4mo ago

wakawaka284mo ago

Concepts make it possible to generate very clear (even user-friendly) template errors.

sunshowers4mo ago

True but you lose out on much of the functionality of templates, right? Also you only get errors when instantiating concretely, rather than getting errors within the template definition.

wakawaka284mo ago

2 more replies

aw16211074mo ago

> but you lose out on much of the functionality of templates, right?

1 more reply

wakawaka284mo ago

I seem to have struck a nerve with my post, which got 4 downvotes so far. Just for saying Rust is not actually better than C++ in this one regard lol.

simonaskOP4mo ago

I think it’s because you misread my comment by skimming over the important parts.

This isn’t about tooling, it’s about language features and type systems.

j / k navigate · click thread line to collapse