C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

82. Use the accepted idioms to really shrink capacity and really erase elements

Summary

Use a diet that works: To really shed excess capacity from a container, use the “swap trick.” To really erase elements from a container, use the erase-remove idiom.

Discussion

Some containers (e.g., vector, string, deque) can end up carrying around extra capacity that’s no longer needed. Although the C++ standard library containers provide no guaranteed way to trim excess capacity, the following “swap trick” idiom works in practice to get rid of excess capacity for such a c of type container:

container<T>( c ).swap( c ); // the shrink-to-fit idiom to shed excess capacity

Or, to empty c out completely, clearing all contained elements and shedding all possible ...