Common Container Abilities
This section covers the common abilities of STL container classes. Most of them are requirements that, in general, every STL container should meet. The three core abilities are as follows:
- All containers provide value rather than reference semantics. Containers copy elements internally when they are inserted rather than managing references to it. Thus, each element of an STL container must be able to be copied. If objects you want to store don't have a public copy constructor, or copying is not useful (for example, because it takes time or elements must be part of multiple containers), the container elements must be pointers or pointer objects that refer to these objects.
- In general, all elements have an order. Thus, you can iterate one or many times over all elements in the same order. Each container type provides operations that return iterators to iterate over the elements. This is the key interface of the STL algorithms.
- In general, operations are not safe. The caller must ensure that the parameters of the operations meet the requirements. Violating these requirements (such as using an invalid index) results in undefined behavior. Usually the STL does not throw exceptions by itself.
If user-defined operations called by the STL containers do throw, the behavior is different.