Array template syntax outside of unique_ptr

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 Ts. I'm wondering what the syntax T[] means generally. Does it get used outside of smart pointers? Is it possible for e.g. vector<T[]> to ever be useful?

T.C. · Accepted Answer · 2015-04-19 10:03:54Z

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?

answered Apr 19, 2015 at 10:03

T.C.

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Johan Lundberg Over a year ago

It surprisingly possible to have an std::vector<int[]> but it seems impossible to use, and the copy semantics would not work.

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