20 General utilities library [utilities]

20.5 Tuples [tuple]

For each tuple assignment operator, an exception is thrown only if the assignment of one of the types in Types throws an exception.

In the function descriptions that follow, let i be in the range [0, sizeof...(Types)) in order,

T_{i}

be the

i^{th}

type in Types, and

U_{i}

be the

i^{th}

type in a template parameter pack named UTypes, where indexing is zero-based.

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

Effects: Assigns each element of u to the corresponding element of *this.

Remarks: This operator is defined as deleted unless is_copy_assignable_v<

T_{i}

> is true for all i.

Returns: *this.

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

Constraints: is_move_assignable_v<

T_{i}

> is true for all i.

Effects: For all i, assigns std::forward<

T_{i}

>(get<i>(u)) to get<i>(*this).

Remarks: The expression inside noexcept is equivalent to the logical and of the following expressions:

is_nothrow_move_assignable_v< $T_{i}$ >

where

T_{i}

is the

i^{th}

type in Types.

Returns: *this.

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

Constraints:

Effects: Assigns each element of u to the corresponding element of *this.

Returns: *this.

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

Constraints:

Effects: For all i, assigns std::forward<

U_{i}

>(get<i>(u)) to get<i>(*this).

Returns: *this.

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

Constraints:

Effects: Assigns u.first to the first element of *this and u.second to the second element of *this.

Returns: *this.

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

Constraints:

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.

Returns: *this.