[tuple.assign]

# 22 General utilities library [[utilities]](./#utilities)

## 22.4 Tuples [[tuple]](tuple#assign)

### 22.4.4 Class template tuple [[tuple.tuple]](tuple.tuple#tuple.assign)

#### 22.4.4.3 Assignment [tuple.assign]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2152)

For each tuple assignment operator, an exception is thrown only if the
assignment of one of the types in Types throws an exception[.](#1.sentence-1)

In the function descriptions that follow, let i be in the range [0, sizeof...​(Types))
in order, Ti be the ith type in Types,
and Ui be the ith type in a
template parameter pack named UTypes, where indexing is zero-based[.](#1.sentence-2)

[🔗](#lib:operator=,tuple)

`constexpr tuple& operator=(const tuple& u);
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2166)

*Effects*: Assigns each element of u to the corresponding
element of *this[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2171)

*Returns*: *this[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2175)

*Remarks*: This operator is defined as deleted unlessis_copy_assignable_v<Ti> is true for all i[.](#4.sentence-1)

[🔗](#lib:operator=,tuple_)

`constexpr const tuple& operator=(const tuple& u) const;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2187)

*Constraints*: (is_copy_assignable_v<const Types> && ...) is true[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2191)

*Effects*: Assigns each element of u to the corresponding element of *this[.](#6.sentence-1)

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2195)

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

[🔗](#lib:operator=,tuple__)

`constexpr tuple& operator=(tuple&& u) noexcept(see below);
`

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2206)

*Constraints*: is_move_assignable_v<Ti> is true for all i[.](#8.sentence-1)

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2210)

*Effects*: For all i, assigns std​::​forward<Ti>(get<i>(u)) toget<i>(*this)[.](#9.sentence-1)

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2215)

*Returns*: *this[.](#10.sentence-1)

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2219)

*Remarks*: The exception specification is equivalent to the logical and of the
following expressions:is_nothrow_move_assignable_v<Ti> where Ti is the ith type in Types[.](#11.sentence-1)

[🔗](#lib:operator=,tuple___)

`constexpr const tuple& operator=(tuple&& u) const;
`

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2235)

*Constraints*: (is_assignable_v<const Types&, Types> && ...) is true[.](#12.sentence-1)

[13](#13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2239)

*Effects*: For all i,
assigns std​::​forward<Ti>(get<i>(u)) to get<i>(*this)[.](#13.sentence-1)

[14](#14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2244)

*Returns*: *this[.](#14.sentence-1)

[🔗](#lib:operator=,tuple____)

`template<class... UTypes> constexpr tuple& operator=(const tuple<UTypes...>& u);
`

[15](#15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2255)

*Constraints*: 

- [(15.1)](#15.1)

sizeof...(Types) equals sizeof...(UTypes) and

- [(15.2)](#15.2)

is_assignable_v<Ti&, const Ui&> is true for all i[.](#15.sentence-1)

[16](#16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2262)

*Effects*: Assigns each element of u to the corresponding element
of *this[.](#16.sentence-1)

[17](#17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2267)

*Returns*: *this[.](#17.sentence-1)

[🔗](#lib:operator=,tuple_____)

`template<class... UTypes> constexpr const tuple& operator=(const tuple<UTypes...>& u) const;
`

[18](#18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2278)

*Constraints*: 

- [(18.1)](#18.1)

sizeof...(Types) equals sizeof...(UTypes) and

- [(18.2)](#18.2)

(is_assignable_v<const Types&, const UTypes&> && ...) is true[.](#18.sentence-1)

[19](#19)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2287)

*Effects*: Assigns each element of u to the corresponding element of *this[.](#19.sentence-1)

[20](#20)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2291)

*Returns*: *this[.](#20.sentence-1)

[🔗](#lib:operator=,tuple______)

`template<class... UTypes> constexpr tuple& operator=(tuple<UTypes...>&& u);
`

[21](#21)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2302)

*Constraints*: 

- [(21.1)](#21.1)

sizeof...(Types) equals sizeof...(UTypes) and

- [(21.2)](#21.2)

is_assignable_v<Ti&, Ui> is true for all i[.](#21.sentence-1)

[22](#22)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2309)

*Effects*: For all i, assigns std​::​forward<Ui>(get<i>(u)) toget<i>(*this)[.](#22.sentence-1)

[23](#23)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2314)

*Returns*: *this[.](#23.sentence-1)

[🔗](#lib:operator=,tuple_______)

`template<class... UTypes> constexpr const tuple& operator=(tuple<UTypes...>&& u) const;
`

[24](#24)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2325)

*Constraints*: 

- [(24.1)](#24.1)

sizeof...(Types) equals sizeof...(UTypes) and

- [(24.2)](#24.2)

(is_assignable_v<const Types&, UTypes> && ...) is true[.](#24.sentence-1)

[25](#25)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2334)

*Effects*: For all i,
assigns std​::​forward<Ui>(get<i>(u)) to get<i>(*this)[.](#25.sentence-1)

[26](#26)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2339)

*Returns*: *this[.](#26.sentence-1)

[🔗](#lib:operator=,tuple________)

`template<class U1, class U2> constexpr tuple& operator=(const pair<U1, U2>& u);
`

[27](#27)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2351)

*Constraints*: 

- [(27.1)](#27.1)

sizeof...(Types) is 2 and

- [(27.2)](#27.2)

is_assignable_v<T0&, const U1&> is true, and

- [(27.3)](#27.3)

is_assignable_v<T1&, const U2&> is true[.](#27.sentence-1)

[28](#28)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2359)

*Effects*: Assigns u.first to the first element of *this and u.second to the second element of *this[.](#28.sentence-1)

[29](#29)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2364)

*Returns*: *this[.](#29.sentence-1)

[🔗](#lib:operator=,tuple_________)

`template<class U1, class U2> constexpr const tuple& operator=(const pair<U1, U2>& u) const;
`

[30](#30)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2375)

*Constraints*: 

- [(30.1)](#30.1)

sizeof...(Types) is 2,

- [(30.2)](#30.2)

is_assignable_v<const T0&, const U1&> is true, and

- [(30.3)](#30.3)

is_assignable_v<const T1&, const U2&> is true[.](#30.sentence-1)

[31](#31)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2386)

*Effects*: Assigns u.first to the first element andu.second to the second element[.](#31.sentence-1)

[32](#32)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2391)

*Returns*: *this[.](#32.sentence-1)

[🔗](#lib:operator=,tuple__________)

`template<class U1, class U2> constexpr tuple& operator=(pair<U1, U2>&& u);
`

[33](#33)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2403)

*Constraints*: 

- [(33.1)](#33.1)

sizeof...(Types) is 2 and

- [(33.2)](#33.2)

is_assignable_v<T0&, U1> is true, and

- [(33.3)](#33.3)

is_assignable_v<T1&, U2> is true[.](#33.sentence-1)

[34](#34)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2411)

*Effects*: Assigns std​::​forward<U1>(u.first) to the first
element of *this and  

std​::​forward<U2>(u.second) to the
second element of *this[.](#34.sentence-2)

[35](#35)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2417)

*Returns*: *this[.](#35.sentence-1)

[🔗](#lib:operator=,tuple___________)

`template<class U1, class U2> constexpr const tuple& operator=(pair<U1, U2>&& u) const;
`

[36](#36)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2428)

*Constraints*: 

- [(36.1)](#36.1)

sizeof...(Types) is 2,

- [(36.2)](#36.2)

is_assignable_v<const T0&, U1> is true, and

- [(36.3)](#36.3)

is_assignable_v<const T1&, U2> is true[.](#36.sentence-1)

[37](#37)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2439)

*Effects*: Assigns std​::​forward<U1>(u.first) to the first element and  

std​::​forward<U2>(u.second) to the second element[.](#37.sentence-2)

[38](#38)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2444)

*Returns*: *this[.](#38.sentence-1)

[🔗](#lib:operator=,tuple____________)

`template<[tuple-like](tuple.like#concept:tuple-like "22.4.3 Concept tuple-like [tuple.like]") UTuple>
  constexpr tuple& operator=(UTuple&& u);
`

[39](#39)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2456)

*Constraints*: 

- [(39.1)](#39.1)

[*different-from*](range.utility.helpers#concept:different-from "25.5.2 Helper concepts [range.utility.helpers]")<UTuple, tuple> ([[range.utility.helpers]](range.utility.helpers "25.5.2 Helper concepts"))
is true,

- [(39.2)](#39.2)

remove_cvref_t<UTuple> is not a specialization of ranges​::​subrange,

- [(39.3)](#39.3)

sizeof...(Types) equals tuple_size_v<remove_cvref_t<UTuple>>, and

- [(39.4)](#39.4)

is_assignable_v<Ti&, decltype(get<i>(std​::​forward<UTuple>(u)))> is true for all i[.](#39.sentence-1)

[40](#40)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2476)

*Effects*: For all i, assigns get<i>(std​::​forward<UTuple>(u)) to get<i>(*this)[.](#40.sentence-1)

[41](#41)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2481)

*Returns*: *this[.](#41.sentence-1)

[🔗](#lib:operator=,tuple_____________)

`template<[tuple-like](tuple.like#concept:tuple-like "22.4.3 Concept tuple-like [tuple.like]") UTuple>
  constexpr const tuple& operator=(UTuple&& u) const;
`

[42](#42)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2493)

*Constraints*: 

- [(42.1)](#42.1)

[*different-from*](range.utility.helpers#concept:different-from "25.5.2 Helper concepts [range.utility.helpers]")<UTuple, tuple> ([[range.utility.helpers]](range.utility.helpers "25.5.2 Helper concepts"))
is true,

- [(42.2)](#42.2)

remove_cvref_t<UTuple> is not a specialization of ranges​::​subrange,

- [(42.3)](#42.3)

sizeof...(Types) equals tuple_size_v<remove_cvref_t<UTuple>>, and

- [(42.4)](#42.4)

is_assignable_v<const Ti&, decltype(get<i>(std​::​forward<UTuple>(u)))> is true for all i[.](#42.sentence-1)

[43](#43)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2513)

*Effects*: For all i, assignsget<i>(std​::​forward<UTuple>(u)) to get<i>(*this)[.](#43.sentence-1)

[44](#44)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L2518)

*Returns*: *this[.](#44.sentence-1)