This partial specialization of the struct template for fundamental types provides a nested type that is not an iterator category, so can be used to control the internal dispatch of function template overloads taking two arguments of the same type.
Synopsis
Declared in <bslstl_vector.h>
template<
class t_ITERATOR,
class t_SENTINEL>
struct Vector_RangeIteratorCategory<t_ITERATOR, t_SENTINEL, true>;