STL Container and Container Adapter Class

C++ Learning Series

While reading “Effective C++” by Scott Meyers, the author says with reference to this particular book, “the STL” means part of C++ STL that works with iterators. But it excludes anything that does not support iterators (like stack, queue, and priority_queue). That got me thinking whats difference between container and container adapter class. Why the distinction.

STL Container:

A STL Container is a template class that directly stores elements and manages their organisation in memory. It also provides full iterator support and support many algorithms.

Common STL Containers:

Examples:

• std::vector – Dynamic array

• std::list – Doubly linked list

• std::deque – Double-ended queue

• std::set, std::map, etc. – Tree-based associative containers

• std::unordered_map, std::unordered_set – Hash-based containers

STL Container Adapter:

A container adapter is a wrapper around an existing container that restricts or modifies its interface to behave like a specific data structure.

Characteristics:

• Uses another container internally (like deque or vector).

• Hides the underlying container's full functionality.

• Provides a simplified or specialized interface (like stack behavior).

Examples:

• std::stack – LIFO stack (typically backed by deque)

• std::queue – FIFO queue (also typically uses deque)

• std::priority_queue – Heap-based priority queue

Basically, a container adapater is a wrapper that uses a container under the hood.