std::common_iterator<I,S>::operator=
template< class I2, class S2 >
requires std::convertible_to<const I2&, I> &&
std::convertible_to<const S2&, S> &&
std::assignable_from<I&, const I2&> &&
std::assignable_from<S&, const S2&>
constexpr common_iterator& operator=( const common_iterator<I2, S2>& x ); |
(since C++20) |
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), ifvar.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
#include <algorithm>
#include <iostream>
#include <iterator>
#include <initializer_list>
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 common_iterator was not |
also made constexpr |
See also
|
(C++20)
|
constructs a new iterator adaptor (public member function) |
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