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

| | | | | ---------------------------------------------------------------------------------------------- | | ----------------------- | | template< class ForwardIt1, class ForwardIt2 > void iter_swap( ForwardIt1 a, ForwardIt2 b ); | | (constexpr since C++20) |

Swaps the values of the elements the given iterators are pointing to.

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

• a or b is not dereferenceable.
• *a is not Swappable with *b.

Contents

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

[edit] Parameters

[edit] Return value

(none)

[edit] Complexity

Constant.

[edit] Notes

This function template models the semantics of the swap operation given by Swappable. That is, overloads of swap found by ADL and the fall back of std::swap are considered.

[edit] Possible implementation

template<class ForwardIt1, class ForwardIt2> constexpr //< since C++20 void iter_swap(ForwardIt1 a, ForwardIt2 b) { using std::swap; swap(*a, *b); }

[edit] Example

The following is an implementation of selection sort in C++.

#include #include #include #include #include   template void selection_sort(ForwardIt begin, ForwardIt end) { for (ForwardIt it = begin; it != end; ++it) std::iter_swap(it, std::min_element(it, end)); }   void println(std::string_view rem, std::vector const& v) { std::cout << rem; for (int e : v) std::cout << e << ' '; std::cout << '\n'; }   template<int min, int max> int rand_int() { static std::uniform_int_distribution dist(min, max); static std::mt19937 gen(std::random_device{}()); return dist(gen); }   int main() { std::vector v; std::generate_n(std::back_inserter(v), 20, rand_int<-9, +9>);   std::cout << std::showpos; println("Before sort: ", v); selection_sort(v.begin(), v.end()); println("After sort: ", v); }

Possible output:

Before sort: -9 -3 +2 -8 +0 -1 +8 -4 -5 +1 -4 -5 +4 -9 -8 -6 -6 +8 -4 -6 After sort: -9 -9 -8 -8 -6 -6 -6 -5 -5 -4 -4 -4 -3 -1 +0 +1 +2 +4 +8 +8

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also

| | swaps the values of two objects (function template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | swaps two ranges of elements (function template) [edit] | | | swaps the objects pointed to by two adjusted underlying iterators (function template) [edit] | | | swaps the objects pointed to by two underlying iterators (function template) [edit] | | | swaps the values referenced by two dereferenceable objects(customization point object)[edit] |