std::swap_ranges - cppreference.com (original) (raw)

1. Exchanges elements between range [first1, last1) and another range of std::distance(first1, last1) elements starting at first2.

2. Same as (1), but executed according to policy.

This overload participates in overload resolution only if all following conditions are satisfied:

If any of the following conditions is satisfied, the behavior is undefined:

• The two ranges overlap.
• There exists a pair of corresponding iterators iter1 and iter2 in the two ranges such that *iter1 is not Swappable with *iter2.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Notes
• 6 Possible implementation
• 7 Example
• 8 See also

[edit] Parameters

[edit] Return value

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

[edit] Complexity

Exactly std::distance(first1, last1) swaps.

[edit] 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.

[edit] 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.

[edit] Possible implementation

template<class ForwardIt1, class ForwardIt2> constexpr //< since C++20 ForwardIt2 swap_ranges(ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2) { for (; first1 != last1; ++first1, ++first2) std::iter_swap(first1, first2);   return first2; }

[edit] Example

Demonstrates swapping of subranges from different containers.

#include #include #include #include   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 v{'a', 'b', 'c', 'd', 'e'}; std::list 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); }

Output:

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

[edit] See also