NAME¶

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

Synopsis¶

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 > (since
requires std::indirectly_swappable<I1, I2> (1) C++20)
constexpr swap_ranges_result<I1, I2>

swap_ranges( I1 first1, S1 last1, I2 first2, S2 last2 );
template< ranges::input_range R1, ranges::input_range R2 >

requires std::indirectly_swappable<ranges::iterator_t<R1>,
ranges::iterator_t<R2>> (2) (since
constexpr swap_ranges_result<ranges::borrowed_iterator_t<R1>, C++20)
ranges::borrowed_iterator_t<R2>>

swap_ranges( R1&& r1, R2&& r2 );

Helper types¶

template< class I1, class I2 > (3) (since
using swap_ranges_result = ranges::in_in_result<I1, I2>; C++20)

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)).
The ranges [first1, last1) and [first2, last2) must 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:

* Explicit template argument lists cannot be specified when calling any of them.
* None of them are visible to argument-dependent lookup.
* When any of them are found by normal unqualified lookup as the name to the left
of the function-call operator, argument-dependent lookup is inhibited.

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

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.

Return value¶

{first1 + M, first2 + M}.

Complexity¶

Exactly M swaps.

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.

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 {};

Example¶

// Run this code

#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

See also¶

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