iter_swap(std::common_iterator)

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_output_iterator (C++20)	forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (deprecated in C++17) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
Algorithm concepts and utilities
Indirect callable concepts
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)	indirect_unary_predicate (C++20) indirect_binary_predicate (C++20)	indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20)	indirectly_copyable_storable (C++20)   indirectly_swappable (C++20) indirectly_comparable (C++20)	permutable (C++20) mergeable (C++20) sortable (C++20)
Utilities
indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
Iterator adaptors
reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter move_sentinel (C++20)	common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) make_const_iterator (C++23) make_const_sentinel (C++23)
Stream iterators istream_iterator    ostream_iterator istreambuf_iterator ostreambuf_iterator	Iterator customization points ranges::iter_move (C++20) ranges::iter_swap (C++20)
Iterator operations advance distance prev (C++11)   next (C++11) ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)	Range access begincbegin (C++11)(C++14) rbegincrbegin (C++14)(C++14)   endcend (C++11)(C++14) rendcrend (C++14)(C++14)   sizessize (C++17)(C++20) empty (C++17) data (C++17)

 

std::common_iterator

Member functions

common_iterator::common_iterator

common_iterator::operator=

common_iterator::operator*common_iterator::operator->

common_iterator::operator++common_iterator::operator++(int)

Non-member functions

operator== (C++20)

operator- (C++20)

iter_move (C++20)

iter_swap (C++20)

Helper classes

incrementable_traits<std::common_iterator> (C++20)

iterator_traits<std::common_iterator> (C++20)

 

template< std::indirectly_swappable<I> I2, class S2 > friend constexpr void     iter_swap( const common_iterator& x,                const std::common_iterator<I2, S2>& y ) noexcept(/*see below*/);		(since C++20)

Swaps the objects pointed to by two underlying iterators. The behavior is undefined if x does not hold an I object or y does not hold an I2 object (i.e. at least one of x and y does not hold an iterator).

The function body is equivalent to ranges::iter_swap(std::get<I>(x.var), std::get<I2>(y.var)).

This function template is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::common_iterator<I,S> is an associated class of the arguments.

Parameters

x, y

-

the iterators to the elements to swap

Return value

(none)

Complexity

Constant.

Exceptions

noexcept specification:  

noexcept(noexcept(ranges::iter_swap(std::declval<const I&>(), std::declval<const I2&>())))

Example

Run this code

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
 
int main()
{
    std::vector<std::string> v1{"1", "2", "3", "4", "5"},
                             v2{"α", "β", "γ", "δ", "ε"};
 
    using CI = std::common_iterator<
                   std::counted_iterator<std::vector<std::string>::iterator>,
                   std::default_sentinel_t
                   >;
 
    CI first1{std::counted_iterator{v1.begin(), 3}};
    CI first2{std::counted_iterator{v2.begin(), 4}};
    CI last{std::default_sentinel};
 
    auto print = [&](auto rem)
    {
        std::cout << rem << "v1 = ";
        std::ranges::copy(v1, std::ostream_iterator<std::string>{std::cout, " "});
        std::cout << "\nv2 = ";
        std::ranges::copy(v2, std::ostream_iterator<std::string>{std::cout, " "});
        std::cout << '\n';
    };
 
    print("Before iter_swap:\n");
 
    for (; first1 != last && first2 != last; ++first1, ++first2)
        iter_swap(first1, first2); // ADL
 
    print("After iter_swap:\n");
}

Output:

Before iter_swap:
v1 = 1 2 3 4 5 
v2 = α β γ δ ε 
After iter_swap:
v1 = α β γ 4 5 
v2 = 1 2 3 δ ε

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

swap	swaps the values of two objects (function template)
swap_ranges	swaps two ranges of elements (function template)
iter_swap	swaps the elements pointed to by two iterators (function template)
iter_swap (C++20)	swaps the values referenced by two dereferenceable objects (customization point object)
iter_swap (C++20)	swaps the objects pointed to by two underlying iterators (function template)