[span.iterators]

# 23 Containers library [[containers]](./#containers)

## 23.7 Views [[views]](views#span.iterators)

### 23.7.2 Contiguous access [[views.contiguous]](views.contiguous#span.iterators)

#### 23.7.2.2 Class template span [[views.span]](views.span#span.iterators)

#### 23.7.2.2.7 Iterator support [span.iterators]

[🔗](#lib:iterator,span)

`using iterator = implementation-defined;
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20893)

The type
models [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")),
meets the *Cpp17RandomAccessIterator* requirements ([[random.access.iterators]](random.access.iterators "24.3.5.7 Random access iterators")),
and
meets the requirements for
constexpr iterators ([[iterator.requirements.general]](iterator.requirements.general "24.3.1 General")),
whose value type is value_type and
whose reference type is reference[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20904)

All requirements on container iterators ([[container.reqmts]](container.reqmts "23.2.2.2 Container requirements")) apply tospan​::​iterator as well[.](#2.sentence-1)

[🔗](#lib:span,begin)

`constexpr iterator begin() const noexcept;
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20915)

*Returns*: An iterator referring to the first element in the span[.](#3.sentence-1)

If empty() is true, then it returns the
same value as end()[.](#3.sentence-2)

[🔗](#lib:span,end)

`constexpr iterator end() const noexcept;
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20928)

*Returns*: An iterator which is the past-the-end value[.](#4.sentence-1)

[🔗](#lib:span,rbegin)

`constexpr reverse_iterator rbegin() const noexcept;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20939)

*Effects*: Equivalent to: return reverse_iterator(end());

[🔗](#lib:span,rend)

`constexpr reverse_iterator rend() const noexcept;
`

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20950)

*Effects*: Equivalent to: return reverse_iterator(begin());