Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Remove all fields from the container.

void
clear();

All references, pointers, or iterators referring to contained elements are invalidated. All past-the-end iterators are also invalidated.

std::distance(this->begin(), this->end()) == 0