std::swap_ranges() algorithm
- od C++20
- od C++17
- do C++17
// (1)
template< class ForwardIt1, class ForwardIt2 >
constexpr ForwardIt2 swap_ranges( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2 );
// (2)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 >
ForwardIt2 swap_ranges( ExecutionPolicy&& policy,
ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2 );
// (1)
template< class ForwardIt1, class ForwardIt2 >
ForwardIt2 swap_ranges( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2 );
// (2)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 >
ForwardIt2 swap_ranges( ExecutionPolicy&& policy,
ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2 );
// (1)
template< class ForwardIt1, class ForwardIt2 >
ForwardIt2 swap_ranges( ForwardIt1 first1, ForwardIt1 last1,
ForwardIt2 first2 );
-
(1) Exchanges elements between range [
first1
;last1
) and another range starting atfirst2
.Precondition: the two ranges [
first1
;last1
) and [first2
;last2
) do not overlap, wherelast2
=std::next(first2, std::distance(first1, last1))
. -
(2) Same as (1), but executed according to
policy
.Overload ResolutionThese overloads participate in overload resolution only if
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(do C++20)std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(od C++20) istrue
.
Parameters
first1 last1 | The first range to swap. |
first2 | The beginning of the second range to swap. |
policy | The execution policy to use. See execution policy for details. |
Type requirements
ForwardIt1 ForwardIt2 | LegacyForwardIterator |
The types of dereferenced ForwardIt1
and ForwardIt2
must meet the requirements of Swappabler.
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 overloads with a template parameter named ExecutionPolicy
report 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 otherExecutionPolicy
, the behavior is implementation-defined. - If the algorithm fails to allocate memory,
std::bad_alloc
is thrown.
Possible implementation
swap_ranges (1)
template<class ForwardIt1, class ForwardIt2>
constexpr ForwardIt2 swap_ranges(ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2)
{
for (; first1 != last1; ++first1, ++first2)
std::iter_swap(first1, first2);
return first2;
}
Notes
Implementations (e.g. MSVC STL) may enable vectorization w hen the iterator type satisfies LegacyContiguousIterator and swapping its value type calls neither non-trivial special member function nor ADL-found swap.
Examples
#include <algorithm>
#include <iostream>
#include <list>
#include <vector>
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
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