std::common_iterator<I,S>::operator=

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Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Range access
(C++11)(C++14)
(C++14)(C++14)
(C++11)(C++14)
(C++14)(C++14)
(C++17)(C++20)
(C++17)
(C++17)
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()

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

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 <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 common_iterator was not also made constexpr

See also

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