[logicchains]

>Some of the flexibility in C++ here is desirable, much of it is either wanking or outright dangerous. C++ will allow a float generic for example, which is obviously a footgun because good luck explaining why Thing<NaN> and Thing<NaN> are different types...

It's not nonsense, there are legitimate use-cases for floating point template params. A classic example is something like generateInlinedVersionOfFunction<someInt, someFloat>() that generates a class or function with some particular values inlined for efficiency. Using nan as a template parameter is stupid, but it's not especially more dangerous than using nan in general, since any issues specific to its compile-time usage will manifest at compile time, not runtime.

It does nobody any favours to just dismiss advanced features Rust doesn't support as dangerous and unnecessary just because most Rust programmers haven't come across a use-case.

[zozbot234]

> It does nobody any favours to just dismiss advanced features Rust doesn't support as dangerous and unnecessary just because most Rust programmers haven't come across a use-case.

I think requiring decidable equality for const generics is a fine approach for a limited MVP like what Rust is going with at present. Sure there are more general settings but they would need dependent types and the user would have to write proofs of type equality/apartness anytime the issue came up in a compile. Seems like a bit of a non-starter for now, even though it's effectively what enables non-trivial logical features like homotopy types.

[tialaramex]

> A classic example is something like generateInlinedVersionOfFunction<someInt, someFloat>() that generates a class or function with some particular values inlined for efficiency.

This smells very bad. Seems like a better choice is a macro, and I understand that in C++ the macros are awful and worth avoiding, but Rust has decent declarative macros for this type of work.

Do you have some real world examples?

[Asooka]

Can't you do that in Rust with a macro?