22 General utilities library [utilities]

22.5 Optional objects [optional]

using iterator = implementation-defined;

This type models contiguous_iterator ([iterator.concept.contiguous]), meets the Cpp17RandomAccessIterator requirements ([random.access.iterators]), and meets the requirements for constexpr iterators ([iterator.requirements.general]), with value type remove_cv_t<T>.

The reference type is T& for iterator.

All requirements on container iterators ([container.reqmts]) apply to optional::iterator.

constexpr iterator begin() const noexcept;

Returns: If has_value() is true, an iterator referring to *val.

Otherwise, a past-the-end iterator value.

constexpr iterator end() const noexcept;

Returns: begin() + has_value().