std::iter_swap
From cppreference.com
| Defined in header <algorithm>
|
||
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:
aorbis not dereferenceable.*ais not Swappable with*b.
Parameters
| a, b | - | iterators to the elements to swap |
| Type requirements | ||
-ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardIterator.
| ||
Complexity
Constant.
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.
Possible implementation
template<class ForwardIt1, class ForwardIt2>
constexpr //< since C++20
void iter_swap(ForwardIt1 a, ForwardIt2 b)
{
using std::swap;
swap(*a, *b);
}
|
Example
The following is an implementation of selection sort in C++.
Run this code
#include <algorithm>
#include <random>
#include <print>
#include <vector>
template<class ForwardIt>
void selection_sort(ForwardIt begin, ForwardIt end)
{
for (ForwardIt it = begin; it != end; ++it)
std::iter_swap(it, std::min_element(it, end));
}
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<int> v;
std::generate_n(std::back_inserter(v), 20, rand_int<-9, +9>);
std::println("Before sort: {}", v);
selection_sort(v.begin(), v.end());
std::println("After sort: {}", v);
}
Possible output:
Before sort: [-3, -8, -9, -9, 0, -6, 7, -3, -2, -8, 1, 5, -7, -8, 4, 8, -6, -7, 3, 6]
After sort: [-9, -9, -8, -8, -8, -7, -7, -6, -6, -3, -3, -2, 0, 1, 3, 4, 5, 6, 7, 8]
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 187 | C++98 | it was unspecified whether swap is used
|
the effect is equivalent to swap(*a, *b)
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See also
| swaps the values of two objects (function template) | |
| swaps two ranges of elements (function template & algorithm function object) | |
(C++20) |
|
(C++20) |
swaps the objects pointed to by two adjusted underlying iterators (function template) |
(C++20) |
swaps the objects pointed to by two underlying iterators (function template) |
(C++20) |
swaps the values referenced by two dereferenceable objects (customization point object) |