std::swap_ranges

template< class ForwardIt1, class ForwardIt2 >
ForwardIt2 swap_ranges( ForwardIt1 first1, ForwardIt1 last1,
                        ForwardIt2 first2 );

template< class ForwardIt1, class ForwardIt2 >
constexpr ForwardIt2 swap_ranges( ForwardIt1 first1, ForwardIt1 last1,
                                  ForwardIt2 first2 );

template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 >
ForwardIt2 swap_ranges( ExecutionPolicy&& policy, 
                        ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2 );

Parameters

Return value

Iterator to the element past the last element exchanged in the range beginning with first2.

Complexity

linear in the distance between first1 and last1.

Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Notes

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

Possible implementation

template<class ForwardIt1, class ForwardIt2>
constexpr ForwardIt2 swap_ranges(ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2)
{
    while (first1 != last1) {
        std::iter_swap(first1++, first2++);
    }
    return first2;
}

Example

#include <list>
#include <vector>
#include <iostream>
#include <algorithm>
 
auto print = [](auto comment, auto const& seq) {
    std::cout << comment;
    for (const auto& e : seq) { std::cout << e << ' '; }
    std::cout << '\n';
};
 
int main()
{
    std::vector<char> v = {'a', 'b', 'c', 'd', 'e'};
    std::list<char> l = {'1', '2', '3', '4', '5'};
 
    print("Before swap_ranges:\n" "v: ", v);
    print("l: ", l);
 
    std::swap_ranges(v.begin(), v.begin()+3, l.begin());
 
    print("After swap_ranges:\n" "v: ", v);
    print("l: ", l);
}

Before swap_ranges:
v: a b c d e 
l: 1 2 3 4 5 
After swap_ranges:
v: 1 2 3 d e 
l: a b c 4 5

See also