[common.iter.const]

# 24 Iterators library [[iterators]](./#iterators)

## 24.5 Iterator adaptors [[predef.iterators]](predef.iterators#common.iter.const)

### 24.5.5 Common iterators [[iterators.common]](iterators.common#common.iter.const)

#### 24.5.5.3 Constructors and conversions [common.iter.const]

[🔗](#lib:common_iterator,constructor)

`constexpr common_iterator(I i);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5548)

*Effects*: Initializes v_ as if by v_{in_place_type<I>, std​::​move(i)}[.](#1.sentence-1)

[🔗](#lib:common_iterator,constructor_)

`constexpr common_iterator(S s);
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5559)

*Effects*: Initializes v_ as if byv_{in_place_type<S>, std​::​move(s)}[.](#2.sentence-1)

[🔗](#lib:common_iterator,constructor__)

`template<class I2, class S2>
  requires [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<const I2&, I> && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<const S2&, S>
    constexpr common_iterator(const common_iterator<I2, S2>& x);
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5573)

*Hardened preconditions*: x.v_.valueless_by_exception() is false[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5577)

*Effects*: Initializes v_ as if byv_{in_place_index<i>, get<i>(x.v_)},
where i is x.v_.index()[.](#4.sentence-1)

[🔗](#lib:operator=,common_iterator)

`template<class I2, class S2>
  requires [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<const I2&, I> && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<const S2&, S> &&
           [assignable_from](concept.assignable#concept:assignable_from "18.4.8 Concept assignable_­from [concept.assignable]")<I&, const I2&> && [assignable_from](concept.assignable#concept:assignable_from "18.4.8 Concept assignable_­from [concept.assignable]")<S&, const S2&>
    constexpr common_iterator& operator=(const common_iterator<I2, S2>& x);
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5593)

*Hardened preconditions*: x.v_.valueless_by_exception() is false[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5597)

*Effects*: Equivalent to:

- [(6.1)](#6.1)

  If v_.index() == x.v_.index(), thenget<i>(v_) = get<i>(x.v_)[.](#6.1.sentence-1)

- [(6.2)](#6.2)

  Otherwise, v_.emplace<i>(get<i>(x.v_))[.](#6.2.sentence-1)

where i is x.v_.index()[.](#6.sentence-2)

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iterators.tex#L5608)

*Returns*: *this[.](#7.sentence-1)