std::ranges::swap_ranges, std::ranges::swap_ranges_result

Since C++20

Header: <algorithm>

  1. Exchanges elements between first range [first1,first1 + M) and second range [first2,first2 + M) via ranges::iter_swap(first1 + i, first2 + i), where M = ranges::min(ranges::distance(first1, last1), ranges::distance(first2, last2)).

# Declarations

Call signature

template< std::input_iterator I1, std::sentinel_for<I1> S1,
std::input_iterator I2, std::sentinel_for<I2> S2 >
requires std::indirectly_swappable<I1, I2>
constexpr swap_ranges_result<I1, I2>
swap_ranges( I1 first1, S1 last1, I2 first2, S2 last2 );

(since C++20)

template< ranges::input_range R1, ranges::input_range R2 >
requires std::indirectly_swappable<ranges::iterator_t<R1>, ranges::iterator_t<R2>>
constexpr swap_ranges_result<ranges::borrowed_iterator_t<R1>,
ranges::borrowed_iterator_t<R2>>
swap_ranges( R1&& r1, R2&& r2 );

(since C++20)

Helper types

template< class I1, class I2 >
using swap_ranges_result = ranges::in_in_result<I1, I2>;

(since C++20)

# Parameters

# Return value

{first1 + M, first2 + M}.

# Notes

Implementations (e.g. MSVC STL) may enable vectorization when the iterator type models contiguous_iterator and swapping its value type calls neither non-trivial special member function nor ADL-found swap.

# Example

#include <algorithm>
#include <iostream>
#include <list>
#include <string_view>
#include <vector>
 
auto print(std::string_view name, auto const& seq, std::string_view term = "\n")
{
    std::cout << name << " : ";
    for (const auto& elem : seq)
        std::cout << elem << ' ';
    std::cout << term;
}
 
int main()
{
    std::vector<char> p {'A', 'B', 'C', 'D', 'E'};
    std::list<char> q {'1', '2', '3', '4', '5', '6'};
 
    print("p", p);
    print("q", q, "\n\n");
 
    // swap p[0, 2) and q[1, 3):
    std::ranges::swap_ranges(p.begin(),
                             p.begin() + 4,
                             std::ranges::next(q.begin(), 1),
                             std::ranges::next(q.begin(), 3));
    print("p", p);
    print("q", q, "\n\n");
 
    // swap p[0, 5) and q[0, 5):
    std::ranges::swap_ranges(p, q);
 
    print("p", p);
    print("q", q);
}

# See also