std::array requires the size to be set at compile-time, while I was talking about arrays whose size is determined at construction-time. Of course std::array is also quite the useful class :-)
But that's the point. You _can_ push_back, or resize, or reserve, etc. etc. My claim is that the more common use case is the one where this _cannot_ happen.
> If you want to get f cy you can also give it a custam allocator
And then nobody will want to use it, because that's not interchangeable with containers vector with the default allocator, and also difficult to understand. I mean, look at PMR allocators, which are not even that custom. They see very little use I'm afraid.
Well, if you want to, I can write you a forwarder-wrapper around a std::vector that would inhibit allocation-inducing operations. Now, getting it into stdlib, that's a different matter entirely...
Also, do I understand correctly that you want both the capacity and the size fixed, i.e., the container's elements have to be pre-constructed and supplied to the constructor via an initializer list?
If you want to get f cy you can also give it a custam allocator and throw an exception if you do this by mistake