Difference between revisions of "cpp/algorithm/move"

Latest revision as of 22:30, 25 March 2024

Defined in header `<algorithm>`
template< class InputIt, class OutputIt > OutputIt move( InputIt first, InputIt last, OutputIt d_first );	(1)	(since C++11) (constexpr since C++20)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > ForwardIt2 move( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first );	(2)	(since C++17)

1) Moves the elements in the range [first, last), to another range beginning at d_first, starting from first and proceeding to last. After this operation the elements in the moved-from range will still contain valid values of the appropriate type, but not necessarily the same values as before the move.

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

This overload participates in overload resolution only if

std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true.	(until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true.	(since C++20)

If d_first is within the range [first, last), the behavior is undefined. In this case, std::move_backward may be used instead.

first, last	-	the range of elements to move
d_first	-	the beginning of the destination range
policy	-	the execution policy to use. See execution policy for details.
Type requirements
- `InputIt` must meet the requirements of LegacyInputIterator.
- `OutputIt` must meet the requirements of LegacyOutputIterator.
- `ForwardIt1, ForwardIt2` must meet the requirements of LegacyForwardIterator.

[edit] Return value

The iterator to the element past the last element moved.

[edit] Complexity

Exactly std::distance(first, last) move assignments.

[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] Possible implementation

template<class InputIt, class OutputIt>
OutputIt move(InputIt first, InputIt last, OutputIt d_first)
{
    for (; first != last; ++d_first, ++first)
        *d_first = std::move(*first);
 
    return d_first;
}

[edit] Notes

When moving overlapping ranges, std::move is appropriate when moving to the left (beginning of the destination range is outside the source range) while std::move_backward is appropriate when moving to the right (end of the destination range is outside the source range).

[edit] Example

The following code moves thread objects (which themselves are not copyable) from one container to another.

Run this code

#include <algorithm>
#include <chrono>
#include <iostream>
#include <iterator>
#include <list>
#include <thread>
#include <vector>
 
void f(int n)
{
    std::this_thread::sleep_for(std::chrono::seconds(n));
    std::cout << "thread " << n << " ended" << std::endl;
}
 
int main()
{
    std::vector<std::jthread> v;
    v.emplace_back(f, 1);
    v.emplace_back(f, 2);
    v.emplace_back(f, 3);
    std::list<std::jthread> l;
 
    // copy() would not compile, because std::jthread is noncopyable
    std::move(v.begin(), v.end(), std::back_inserter(l));
}

Output:

thread 1 ended
thread 2 ended
thread 3 ended

[edit] See also

move_backward (C++11)	moves a range of elements to a new location in backwards order (function template) [edit]
move (C++11)	converts the argument to an xvalue (function template) [edit]
ranges::move (C++20)	moves a range of elements to a new location (niebloid)[edit]

@@ Line 2: / Line 2: @@
 {{cpp/algorithm/navbar}}
 {{dcl begin}}
-{{dcl header | algorithm}}
+{{dcl header|algorithm}}
-{{dcl | notes={{mark since c++11}} |
+{{dcl|num=1|since=c++11|notes={{mark constexpr since c++20}}|
 template< class InputIt, class OutputIt >
-OutputIt move( InputIt first, InputIt last, OutputIt d_first );
+OutputIt move( InputIt first, InputIt last,
+               OutputIt d_first );
+}}
+{{dcl|num=2|since=c++17|
+template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 >
+ForwardIt2 move( ExecutionPolicy&& policy,
+                 ForwardIt1 first, ForwardIt1 last,
+                 ForwardIt2 d_first );
 }}
 {{dcl end}}
-Moves the elements in the range {{tt|[first, last)}}, to another range beginning at {{tt|d_first}}. After this operation the elements in the moved-from range will still contain valid values of the appropriate type, but not necessarily the same values as before the move.
+@1@ Moves the elements in the range {{range|first|last}}, to another range beginning at {{c|d_first}}, starting from first and proceeding to {{c|last}}. After this operation the elements in the moved-from range will still contain valid values of the appropriate type, but not necessarily the same values as before the move.
+@2@ Same as {{v|1}}, but executed according to {{c|policy}}.
+@@ {{cpp/algorithm/parallel overload precondition}}
+If {{c|d_first}} is within the range {{range|first|last}}, the behavior is undefined. In this case, {{lc|std::move_backward}} may be used instead.
 ===Parameters===
 {{par begin}}
-{{par | first, last | the range of elements to move}}
+{{par|first, last|the range of elements to move}}
-{{par | d_first | the beginning of the destination range. If {{tt|d_first}} is within {{tt|[first, last)}}, {{lc|std::move_backward}} must be used instead of [[cpp/algorithm/move#top | <!--Manually apply syntax highlighting while avoiding automatic hyperlinking to the utility function rather than the algorithm--><span class="mw-geshi cpp source-cpp">std::move</span>]]. }}
+{{par|d_first|the beginning of the destination range}}
+{{par exec pol}}
 {{par hreq}}
-{{par req concept | InputIt | InputIterator}}
+{{par req named|InputIt|InputIterator}}
-{{par req concept | OutputIt | OutputIterator}}
+{{par req named|OutputIt|OutputIterator}}
+{{par req named|ForwardIt1, ForwardIt2|ForwardIterator}}
 {{par end}}
 ===Return value===
-Output iterator to the element past the last element moved ({{c|d_first + (last - first)}})
+The iterator to the element past the last element moved.
 ===Complexity===
-Exactly {{tt|last - first}} move assignments.
+Exactly {{c|std::distance(first, last)}} move assignments.
+===Exceptions===
+{{cpp/algorithm/parallel exceptions reporting behavior|singular=yes}}
 ===Possible implementation===
-{{eq fun | 1=
+{{eq fun|1=
 template<class InputIt, class OutputIt>
-OutputIt move(InputIt first, InputIt last,
+OutputIt move(InputIt first, InputIt last, OutputIt d_first)
-                    OutputIt d_first)
 {
-     while (first != last) {
+     for (; first != last; ++d_first, ++first)
-         *d_first++ = std::move(*first++);
+         *d_first = std::move(*first);
-     }
      return d_first;
 }
 }}
+===Notes===
+When moving overlapping ranges, {{tt|std::move}} is appropriate when moving to the left (beginning of the destination range is outside the source range) while {{lc|std::move_backward}} is appropriate when moving to the right (end of the destination range is outside the source range).
 ===Example===
-<p>The following code moves thread objects (which themselves are not copyable) from one container to another.</p>
+The following code moves thread objects (which themselves are not copyable) from one container to another.
-<div dir="ltr" class="mw-geshi" style="text-align: left;">
+{{example
-{{c|
+|code=
+#include <algorithm>
+#include <chrono>
 #include <iostream>
-#include <vector>
-#include <list>
 #include <iterator>
+#include <list>
 #include <thread>
-#include <chrono>
+#include <vector>
 void f(int n)
 {
      std::this_thread::sleep_for(std::chrono::seconds(n));
-     std::cout << "thread " << n << " ended" << '\n';
+     std::cout << "thread " << n << " ended" << std::endl;
 }
 int main()
 {
-     std::vector<std::thread> v;
+     std::vector<std::jthread> v;
      v.emplace_back(f, 1);
      v.emplace_back(f, 2);
      v.emplace_back(f, 3);
-     std::list<std::thread> l;
+     std::list<std::jthread> l;
-     // copy() would not compile, because std::thread is noncopyable
-}}
+     // copy() would not compile, because std::jthread is noncopyable
-<span class="mw-geshi cpp source-cpp">&nbsp;&nbsp;&nbsp;
+    std::move(v.begin(), v.end(), std::back_inserter(l));
-[[cpp/algorithm/move#top | std::move</span>]]{{c|(v.begin(), v.end(), std::back_inserter(l));
-    for(auto& t : l) t.join();
 }
-}}
+|output=
-</div>
+thread 1 ended
-Output:
-{{source | lang=text |thread 1 ended
 thread 2 ended
 thread 3 ended
@@ Line 81: / Line 96: @@
 ===See also===
 {{dsc begin}}
-{{dsc inc | cpp/algorithm/dsc move_backward}}
+{{dsc inc|cpp/algorithm/dsc move_backward}}
-{{dsc inc | cpp/utility/dsc move}}
+{{dsc inc|cpp/utility/dsc move}}
+{{dsc inc|cpp/algorithm/ranges/dsc move}}
 {{dsc end}}
-[[de:cpp/algorithm/move]]
+{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
-[[es:cpp/algorithm/move]]
-[[fr:cpp/algorithm/move]]
-[[it:cpp/algorithm/move]]
-[[ja:cpp/algorithm/move]]
-[[pt:cpp/algorithm/move]]
-[[ru:cpp/algorithm/move]]
-[[zh:cpp/algorithm/move]]

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Difference between revisions of "cpp/algorithm/move"

Latest revision as of 22:30, 25 March 2024

Contents

[edit] Parameters