Is begin() == end() for any empty() vector?

Question

I have long assumed that for any empty std::vector V, V.begin() == V.end(). Yet I see nothing in the C++ specification that states this to always be true. Is it necessarily true or does it just happen to be true on most implementations?

Answer 1

Yes, that's what the standard requires it to be for empty() for any container.

§ 23.2.1 Table 96 of the C++11 standard says:

Expression	Return Type	Operational Semantics
a.empty()	Convertible to bool	a.begin() == a.end()