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

From cppreference.com
< cpp‎ | algorithm‎ | ranges
 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms: std::ranges::copy, std::ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
(C++11)(C++11)(C++11)
(C++17)
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
(C++11)
Binary search operations
Set operations (on sorted ranges)
Heap operations
(C++11)
Minimum/maximum operations
(C++11)
(C++17)

Permutations
Numeric operations
C library
 
Constrained algorithms
Non-modifying sequence operations
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
Binary search operations
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Permutations
 
Defined in header <algorithm>
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 ranges::swap_ranges_result<I1, I2>

      ranges::swap_ranges( I1 first1, S1 last1, I2 first2, S2 last2 );
(1) (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 ranges::swap_ranges_result<ranges::borrowed_iterator_t<R1>,
                                         ranges::borrowed_iterator_t<R2>>

      ranges::swap_ranges( R1&& r1, R2&& r2 );
(2) (since C++20)
Helper types
template<class I1, class I2>
  using swap_ranges_result = ranges::in_in_result<I1, I2>;
(3) (since C++20)
1) Exchanges elements between first range [first1, first1 + M) and second range [first2, first2 + M), where M = min(last1 - first1, last2 - first2). Precondition: the two ranges [first1, last1) and [first2, last2) do not overlap.
2) Same as (1), but uses r1 as the first range and r2 as the second range, as if using ranges::begin(r1) as first1, ranges::end(r1) as last1, ranges::begin(r2) as first2, and ranges::end(r2) as last2.

The function-like entities described on this page are niebloids, that is:

In practice, they may be implemented as function objects, or with special compiler extensions.

Contents

[edit] Parameters

first1, last1 - the first range of elements to swap
first2, last2 - the second range of elements to swap
r1 - the first range of elements to swap
r2 - the second range of elements to swap.

[edit] Return value

An object {first1 + M, first2 + M}.

[edit] Complexity

Exactly M swaps.

[edit] Possible implementation

struct swap_ranges_fn {
 
  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 ranges::swap_ranges_result<I1, I2>
        operator() ( I1 first1, S1 last1, I2 first2, S2 last2 ) const {
            for (; !(first1 == last1 or first2 == last2); ++first1, ++first2)
                ranges::iter_swap(first1, first2);
            return {std::move(first1), std::move(first2)};
        }
 
  template<ranges::input_range R1, ranges::input_range R2>
    requires std::indirectly_swappable<ranges::iterator_t<R1>, ranges::iterator_t<R2>>
      constexpr ranges::swap_ranges_result<ranges::borrowed_iterator_t<R1>,
                                           ranges::borrowed_iterator_t<R2>>
        operator() ( R1&& r1, R2&& r2 ) const {
            return (*this)(ranges::begin(r1), ranges::end(r1),
                           ranges::begin(r2), ranges::end(r2));
        }
};
 
inline constexpr swap_ranges_fn swap_ranges{};

[edit] 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);
}

Output:

p : A B C D E
q : 1 2 3 4 5 6
 
p : 2 3 C D E
q : 1 A B 4 5 6
 
p : 1 A B 4 5
q : 2 3 C D E 6

[edit] See also

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