std::ranges::uninitialized_copy, std::ranges::uninitialized_copy_result - cppreference.com (original) (raw)

Let \(\scriptsize N\)N be ranges::min(ranges::distance(ifirst, ilast), ranges::distance(ofirst, olast)).

1. Constructs \(\scriptsize N\)N elements elements from the range [ifirst, ilast) to an uninitialized memory area [ofirst, olast) as if by

for (; ifirst != ilast && ofirst != olast; ++ofirst, (void)++ifirst)
``::new (voidify(*ofirst)) std::remove_reference_t<std::iter_reference_t<O>>(*ifirst);
return {std::move(ifirst), ofirst};

If an exception is thrown during the initialization, the objects already constructed are destroyed in an unspecified order.

If [ofirst, olast) overlaps with [ifirst, ilast), the behavior is undefined.

The function-like entities described on this page are algorithm function objects (informally known as 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.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Notes
• 6 Possible implementation
• 7 Example
• 8 Defect reports
• 9 See also

[edit] Parameters

[edit] Return value

As described above.

[edit] Complexity

\(\scriptsize\mathcal{O}(N)\)𝓞(N).

[edit] Exceptions

Any exception thrown on construction of the elements in the destination range.

[edit] Notes

An implementation may improve the efficiency of ranges::uninitialized_copy if the value type of the output range is TrivialType.

[edit] Possible implementation

struct uninitialized_copy_fn { template<std::input_iterator I, std::sentinel_for S1, no-throw-forward-iterator O, no-throw-sentinel-for S2> requires std::constructible_from<std::iter_value_t, std::iter_reference_t> constexpr ranges::uninitialized_copy_result<I, O> operator()(I ifirst, S1 ilast, O ofirst, S2 olast) const { O current{ofirst}; try { for (; !(ifirst == ilast or current == olast); ++ifirst, ++current) ranges::construct_at(std::addressof(*current), *ifirst); return {std::move(ifirst), std::move(current)}; } catch (...) // rollback: destroy constructed elements { for (; ofirst != current; ++ofirst) ranges::destroy_at(std::addressof(*ofirst)); throw; } }   template<ranges::input_range IR, no-throw-forward-range OR> requires std::constructible_from<ranges::range_value_t, constexpr ranges::range_reference_t> ranges::uninitialized_copy_result<ranges::borrowed_iterator_t, ranges::borrowed_iterator_t> operator()(IR&& in_range, OR&& out_range) const { return (*this)(ranges::begin(in_range), ranges::end(in_range), ranges::begin(out_range), ranges::end(out_range)); } };   inline constexpr uninitialized_copy_fn uninitialized_copy{};

[edit] Example

Output:

{"This", "is", "an", "example"};

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also