The class template pointer_traits supplies a uniform interface to certain attributes of pointer-like types.
namespace std {
template <class Ptr> struct pointer_traits {
using pointer = Ptr;
using element_type = see below;
using difference_type = see below;
template <class U> using rebind = see below;
static pointer pointer_to(see below r);
};
template <class T> struct pointer_traits<T*> {
using pointer = T*;
using element_type = T;
using difference_type = ptrdiff_t;
template <class U> using rebind = U*;
static pointer pointer_to(see below r) noexcept;
};
}
using element_type = see below;
Type: Ptr::element_type if the qualified-id Ptr::element_type is valid and denotes a type ([temp.deduct]); otherwise, T if Ptr is a class template instantiation of the form SomePointer<T, Args>, where Args is zero or more type arguments; otherwise, the specialization is ill-formed.
using difference_type = see below;
Type: Ptr::difference_type if the qualified-id Ptr::difference_type is valid and denotes a type ([temp.deduct]); otherwise, ptrdiff_t.
template <class U> using rebind = see below;
Alias template: Ptr::rebind<U> if the qualified-id Ptr::rebind<U> is valid and denotes a type ([temp.deduct]); otherwise, SomePointer<U, Args> if Ptr is a class template instantiation of the form SomePointer<T, Args>, where Args is zero or more type arguments; otherwise, the instantiation of rebind is ill-formed.
static pointer pointer_traits::pointer_to(see below r);
static pointer pointer_traits<T*>::pointer_to(see below r) noexcept;
Remarks: If element_type is (possibly cv-qualified) void, the type of r is unspecified; otherwise, it is element_type&.
Returns: The first member function returns a pointer to r obtained by calling Ptr::pointer_to(r) through which indirection is valid; an instantiation of this function is ill-formed if Ptr does not have a matching pointer_to static member function. The second member function returns addressof(r).