std::experimental::ranges::difference_type (3) Linux Manual Page

std::experimental::ranges::difference_type – std::experimental::ranges::difference_type

Synopsis

Defined in header<experimental / ranges / iterator>

    template <class I>
    (1)

        struct difference_type {
};

template <class T>
(2)

    struct difference_type<T *>;

template <class T>
(3)

    struct difference_type<const T> : difference_type<std::decay_t<T>> {
};

template <class T>

requires requires
{
    typename T::difference_type;
}
(4)

    struct difference_type<T>;

template <class T>

requires !requires
{
    typename T::difference_type;
}
&&(5)

    requires(const T &a, const T &b)
{
    {
        a - b
        } -> Integral;
}

struct difference_type<T>;

Computes the associated difference type of the type I, if any. Users may specialize difference_type for a program-defined type.
1) Primary template is an empty struct.
2) Specialization for pointers. If T is an object type, provides a member type type equal to std::ptrdiff_t. Otherwise, there is no member type.
3) Specialization for const-qualified types.
4) Specialization for types that define a public and accessible member type difference_type. Provides a member type type equal to T::difference_type.
5) Specialization for types that do not define a public and accessible member type difference_type but do support subtraction. Provides a member type type equal to std::make_signed_t<decltype(std::declval<T>() – std::declval<T>())>.
Helper alias template

template< class T >                                                   (ranges TS)

using difference_type_t = typename ranges::difference_type<T>::type;

Example

 This section is incomplete
 Reason: no example

See also

                    specifies that a Semiregular type can be incremented with pre- and post-increment operators
WeaklyIncrementable (concept)
                    compatibility traits class that collects an iterator’s associated types
iterator_traits (alias template)