唯一性数组之外的数组模板语法

Question

The syntax std::unique_ptr<T[]> can be used describe the (templated) type of a unique_ptr whose underlying raw pointer is pointing to an array of T s. I'm wondering what the syntax T[] means generally. Does it get used outside of smart pointers? Is it possible for eg vector<T[]> to ever be useful?

Answer 1

It means "array of unknown bound of T ". You might see such a type in function signatures:

void f(int arr[]);

In a declaration of an array defined elsewhere:

extern int arr[];

And obviously, as a type parameter to a template like unique_ptr (or, some time in the future, shared_ptr too). It's an incomplete type, so its usefulness can be rather limited.

vector<T[]> is unlikely to be useful. If you don't know how many elements are in the array, then how could you have a container of them?