# std::ranges::move, std::ranges::move_result

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< cpp‎ | algorithm‎ | ranges

Defined in header `<algorithm>` |  |
Call signature |  |
template< std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O > requires std::indirectly_movable<I, O> constexpr move_result<I, O> move( I first, S last, O result ); | (1) | (since C++20)
template< ranges::input_range R, std::weakly_incrementable O > requires std::indirectly_movable<ranges::iterator_t<R>, O> constexpr move_result<ranges::borrowed_iterator_t<R>, O> move( R&& r, O result ); | (2) | (since C++20)
Helper types |  |
template< class I, class O > using move_result = ranges::in_out_result<I, O>; | (3) | (since C++20)

1) Moves the elements in the range, defined by `[`first`,` last`)`, to another range beginning at result. The behavior is undefined if result is within the range `[`first`,` last`)`. In such a case, ranges::move_backward may be used instead.
2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as first, and ranges::end(r) as last.

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.

The function-like entities described on this page are niebloids, that is:

- Explicit template argument lists cannot be specified when calling any of them.
- None of them are visible to argument-dependent lookup.
- When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

In practice, they may be implemented as function objects, or with special compiler extensions.

### Parameters

first | - | the beginning of the range of elements to move
last | - | the end of the range of elements to move
r | - | the range of the elements to move
result | - | the beginning of the destination range

### Return value

{last, result + N}, where

1) N = ranges::distance(first, last).
2) N = ranges::distance(r).

### Complexity

Exactly N move assignments.

### Notes

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

### Possible implementation

    struct move_fn
    {
        template<std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O>
        requires std::indirectly_movable<I, O>
        constexpr ranges::move_result<I, O>
            operator()(I first, S last, O result) const
        {
            for (; first != last; ++first, ++result)
                *result = ranges::iter_move(first);
            return {std::move(first), std::move(result)};
        }
        template<ranges::input_range R, std::weakly_incrementable O>
        requires std::indirectly_movable<ranges::iterator_t<R>, O>
        constexpr ranges::move_result<ranges::borrowed_iterator_t<R>, O>
            operator()(R&& r, O result) const
        {
            return (*this)(ranges::begin(r), ranges::end(r), std::move(result));
        }
    };

    inline constexpr move_fn move {};

### Example

The following code moves thread objects (which themselves are non copyable) from one container to another.

Run this code

    #include <algorithm>
    #include <chrono>
    #include <iostream>
    #include <iterator>
    #include <list>
    #include <thread>
    #include <vector>
    using namespace std::literals::chrono_literals;

    void f(std::chrono::milliseconds n)
    {
        std::this_thread::sleep_for(n);
        std::cout << "thread with n=" << n.count() << "ms ended" << std::endl;
    }

    int main()
    {
        std::vector<std::jthread> v;
        v.emplace_back(f, 400ms);
        v.emplace_back(f, 600ms);
        v.emplace_back(f, 800ms);

        std::list<std::jthread> l;

        // std::ranges::copy() would not compile, because std::jthread is non-copyable
        std::ranges::move(v, std::back_inserter(l));
    }

Output:

    thread with n=400ms ended
    thread with n=600ms ended
    thread with n=800ms ended

### See also

ranges::move_backward (C++20) | moves a range of elements to a new location in backwards order (niebloid)
ranges::copy ranges::copy_if (C++20)(C++20) | copies a range of elements to a new location (niebloid)
ranges::copy_backward (C++20) | copies a range of elements in backwards order (niebloid)
move (C++11) | moves a range of elements to a new location (function template)
move (C++11) | obtains an rvalue reference (function template)

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