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# std::uninitialized_copy

From cppreference.com
< cpp‎ | memory

Defined in header `<memory>` |  |
template< class InputIt, class ForwardIt > ForwardIt uninitialized_copy( InputIt first, InputIt last, ForwardIt d_first ); |  |

Copies elements from the range `[first, last)` to an uninitialized memory area beginning at `d_first`. The elements in the uninitialized area are constructed using copy constructor.

### [edit] Parameters

first, last | - | the range of the elements to copy
d_first | - | the beginning of the destination range
Type requirements
- `InputIt` must meet the requirements of `InputIterator`.
- `ForwardIt` must meet the requirements of `ForwardIterator`.

### [edit] Return value

Iterator to the element past the last element copied.

### [edit] Complexity

Linear in the distance between `first` and `last`

### [edit] Possible implementation

    template<class InputIt, class ForwardIt>
    ForwardIt uninitialized_copy(InputIt first, InputIt last, ForwardIt d_first)
    {
        typedef typename std::iterator_traits<ForwardIt>::value_type Value;
        for (; first != last; ++first, ++d_first) {
            ::new (static_cast<void*>(&*d_first)) Value(*first);
        }
        return d_first;
    }

| This section is incomplete Reason: The above implementation is only valid if constructing the `Value` does not throw. If it throws, then all previously constructed objects must be destructed.

### [edit] Example

Run this code

    #include <algorithm>
    #include <iostream>
    #include <memory>
    #include <string>
    #include <tuple>

    int main()
    {
        std::vector<std::string> v = {"This", "is", "an", "example"};

        std::string* p;
        std::size_t sz;
        std::tie(p, sz)  = std::get_temporary_buffer<std::string>(v.size());
        sz = std::min(sz, v.size());

        std::uninitialized_copy(v.begin(), v.begin() + sz, p);

        for (std::string* i = p; i != p+sz; ++i) {
            std::cout << *i << ' ';
            i->~basic_string<char>();
        }
        std::return_temporary_buffer(p);
    }

Output:

    This is an example

### [edit] See also

uninitialized_copy_n (C++11) | copies a number of objects to an uninitialized area of memory (function template) [edit]

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- Todo with reason