std::swap_ranges

 

C++

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Technical Specifications

 

Algorithm library

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is_execution_policy	sequentialparpar_vec	sequential_execution_policyparallel_execution_policyparallel_vector_execution_policy
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all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each for_each_n (C++17)	countcount_if mismatch equal lexicographical_compare	findfind_iffind_if_not (C++11) find_end find_first_of	adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) transform	fill fill_n generate generate_n swap iter_swap swap_ranges sample (C++17)	removeremove_if replacereplace_if reverse rotate unique random_shuffle (until C++17)	remove_copyremove_copy_if replace_copyreplace_copy_if reverse_copy rotate_copy unique_copy shuffle (C++11)
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uninitialized_copy	uninitialized_copy_n	uninitialized_fill	uninitialized_fill_n
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is_partitioned (C++11) partition_point (C++11)	partition partition_copy (C++11)	stable_partition
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C library
qsort	bsearch

 

Defined in header <algorithm>
template< class ForwardIt1, class ForwardIt2 > ForwardIt2 swap_ranges( ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2 );	(1)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > ForwardIt2 swap_ranges( ExecutionPolicy&& policy, ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2 );	(2)	(since C++17)

1) Exchanges elements between range [first1, last1) and another range starting at first2.

2) Same as (1), but executed according to policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first1, last1	-	the first range of elements to swap
first2	-	beginning of the second range of elements to swap
policy	-	the execution policy to use. See execution policy for details.
Type requirements
- ForwardIt1, ForwardIt2 must meet the requirements of ForwardIterator.
- The types of dereferenced ForwardIt1 and ForwardIt2 must meet the requirements of Swappable

Return value

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

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,

• if policy is std::parallel_vector_execution_policy, std::terminate is called
• if policy is std::sequential_execution_policy or std::parallel_execution_policy, the algorithm exits with an std::exception_list containing all uncaught exceptions. If there was only one uncaught exception, the algorithm may rethrow it without wrapping in std::exception_list. It is unspecified how much work the algorithm will perform before returning after the first exception was encountered.
• if policy is some other type, the behavior is implementation-defined

• If the algorithm fails to allocate memory (either for itself or to construct an std::exception_list when handling a user exception), std::bad_alloc is thrown.

Possible implementation

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

Example

Demonstrates swapping of subranges from different containers

Run this code

#include <algorithm>
#include <list>
#include <vector>
#include <iostream>
int main()
{
    std::vector<int> v = {1, 2, 3, 4, 5};
    std::list<int> l = {-1, -2, -3, -4, -5};
 
    std::swap_ranges(v.begin(), v.begin()+3, l.begin());
 
    for(int n : v)
       std::cout << n << ' ';
    std::cout << '\n';
    for(int n : l)
       std::cout << n << ' ';
    std::cout << '\n';
}

Output:

-1 -2 -3 4 5
1 2 3 -4 -5

Complexity

linear in the distance between first and last

See also

iter_swap	swaps the elements pointed to by two iterators (function template)
swap	swaps the values of two objects (function template)
std::experimental::parallel::swap_ranges (parallelism TS)	parallelized version of std::swap_ranges (function template)