T

The type of the elements stored in the circular_buffer. The T has to be Assignable and CopyConstructible. Moreover T has to be DefaultConstructible if supplied as a default parameter when invoking some of the circular_buffer's methods, e.g. insert(iterator pos, const value_type& item = value_type()). And EqualityComparable and/or LessThanComparable if the circular_buffer will be compared with another container.

Alloc

The allocator type used for all internal memory management. The Alloc has to meet the allocator requirements imposed by STL.