NAME¶

std::common_iterator::operator= - std::common_iterator::operator=

Synopsis¶

template< class I2, class S2 >

requires std::convertible_to<const I2&, I> &&
std::convertible_to<const S2&, S> &&
std::assignable_from<I&, const I2&> && (since C++20)
std::assignable_from<S&, const S2&>

constexpr common_iterator& operator=( const common_iterator<I2, S2>&
x );

Assigns the underlying std::variant member object var from that of x.

Let i is x.var.index(). Then, this assignment is equivalent to:

* std::get<i>(var) = std::get<i>(x.var), if var.index() == i,
* var.emplace<i>(std::get<i>(x.var)) otherwise.

The behavior is undefined if x is in an invalid state, that is,
x.var.valueless_by_exception() is equal to true.

Parameters¶

x - iterator adaptor to assign from

Return value¶

*this

Example¶

// Run this code

#include <algorithm>
#include <initializer_list>
#include <iostream>
#include <iterator>

int main()
{
const auto il = {1, 2, 3, 4, 5, 6};
using CI = std::common_iterator<
std::counted_iterator<std::initializer_list<int>::iterator>,
std::default_sentinel_t>;
CI first{std::counted_iterator{std::next(begin(il), 1), ssize(il) - 1}};
const CI first2{std::counted_iterator{std::next(begin(il), 2), ssize(il) - 2}};
const CI last{std::default_sentinel};
std::copy(first, last, std::ostream_iterator<int>{std::cout, " "});
std::cout << '\n';
first = first2;
std::copy(first, last, std::ostream_iterator<int>{std::cout, " "});
std::cout << '\n';
}

Output:¶

2 3 4 5 6
3 4 5 6

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3574 C++20 variant was fully constexpr (P2231R1) but also made constexpr
common_iterator was not

See also¶

constructor constructs a new iterator adaptor
(C++20) (public member function)