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cppdraft/optional/iterators.md

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+[optional.iterators]
+
+# 22 General utilities library [[utilities]](./#utilities)
+
+## 22.5 Optional objects [[optional]](optional#iterators)
+
+### 22.5.3 Class template optional [[optional.optional]](optional.optional#optional.iterators)
+
+#### 22.5.3.6 Iterator support [optional.iterators]
+
+[🔗](#lib:iterator,optional)
+
+`using iterator       = implementation-defined;
+using const_iterator = implementation-defined;
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4059)
+
+These types
+model [contiguous_iterator](iterator.concept.contiguous#concept:contiguous_iterator "24.3.4.14 Concept contiguous_­iterator [iterator.concept.contiguous]") ([[iterator.concept.contiguous]](iterator.concept.contiguous "24.3.4.14 Concept contiguous_­iterator")),
+meet the [*Cpp17RandomAccessIterator*](random.access.iterators#:Cpp17RandomAccessIterator "24.3.5.7 Random access iterators [random.access.iterators]") requirements ([[random.access.iterators]](random.access.iterators "24.3.5.7 Random access iterators")), and
+meet the requirements for constexpr iterators ([[iterator.requirements.general]](iterator.requirements.general "24.3.1 General")),
+with value type remove_cv_t<T>[.](#1.sentence-1)
+
+The reference type is T& for iterator andconst T& for const_iterator[.](#1.sentence-2)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4068)
+
+All requirements on container iterators ([[container.reqmts]](container.reqmts "23.2.2.2 Container requirements")) apply tooptional​::​iterator and optional​::​const_iterator as well[.](#2.sentence-1)
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4072)
+
+Any operation that initializes or destroys the contained value of an optional object invalidates all iterators into that object[.](#3.sentence-1)
+
+[🔗](#lib:begin,optional)
+
+`constexpr iterator begin() noexcept;
+constexpr const_iterator begin() const noexcept;
+`
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4083)
+
+*Returns*: If has_value() is true,
+an iterator referring to the contained value[.](#4.sentence-1)
+
+Otherwise, a past-the-end iterator value[.](#4.sentence-2)
+
+[🔗](#lib:end,optional)
+
+`constexpr iterator end() noexcept;
+constexpr const_iterator end() const noexcept;
+`
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4097)
+
+*Returns*: begin() + has_value()[.](#5.sentence-1)