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std::move

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< cpp‎ | algorithm
Revision as of 21:45, 31 May 2013 by P12bot (Talk | contribs)

 
 
 
Defined in header <algorithm>
template< class InputIt, class OutputIt >
OutputIt move( InputIt first, InputIt last, OutputIt d_first );
(since C++11)

Moves the elements in the range [first, last), to another range beginning at 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.

Contents

Parameters

first, last - the range of elements to move
d_first - the beginning of the destination range. If d_first is within [first, last), std::move_backward must be used instead of std::move.
Type requirements
-
InputIt must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

Return value

Output iterator to the element past the last element moved (d_first + (last - first))

Complexity

Exactly last - first move assignments.

Possible implementation

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

Example

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

#include <iostream>
#include <vector>
#include <list>
#include <iterator>
#include <thread>
#include <chrono>

void f(int n)
{
    std::this_thread::sleep_for(std::chrono::seconds(n));
    std::cout << "thread " << n << " ended" << '\n';
}

int main()
{
    std::vector<std::thread> v;
    v.emplace_back(f, 1);
    v.emplace_back(f, 2);
    v.emplace_back(f, 3);
    std::list<std::thread> l;
    // copy() would not compile, because std::thread is noncopyable
    std::move(v.begin(), v.end(), std::back_inserter(l));
    for(auto& t : l) t.join();
}

Output:

thread 1 ended
thread 2 ended
thread 3 ended

See also

moves a range of elements to a new location in backwards order
(function template) [edit]
(C++11)
obtains an rvalue reference
(function template) [edit]