[iterator.concepts.general] (original) (raw)

24 Iterators library [iterators]

24.3 Iterator requirements [iterator.requirements]

24.3.4 Iterator concepts [iterator.concepts]

24.3.4.1 General [iterator.concepts.general]

For a type I, let ITER_TRAITS(I) denote the type I if iterator_traits<I> names a specialization generated from the primary template.

Otherwise, ITER_TRAITS(I) denotesiterator_traits<I>.

• If the qualified-id ITER_TRAITS(I)​::​iterator_concept is valid and names a type, then ITER_CONCEPT(I) denotes that type.
• Otherwise, if the qualified-id ITER_TRAITS(I)​​::​iterator_category is valid and names a type, then ITER_CONCEPT(I) denotes that type.
• Otherwise, if iterator_traits<I> names a specialization generated from the primary template, then ITER_CONCEPT(I) denotes random_access_iterator_tag.
• Otherwise, ITER_CONCEPT(I) does not denote a type.

[Note 1:

ITER_TRAITS enables independent syntactic determination of an iterator's category and concept.

— _end note_]

[Example 1:

struct I { using value_type = int;using difference_type = int;int operator*() const; I& operator++(); I operator++(int); I& operator--(); I operator--(int);bool operator==(I) const;}; iterator_traits<I>​::​iterator_category denotes input_iterator_tag, and ITER_CONCEPT(I) denotes random_access_iterator_tag.

— _end example_]