std::ranges::uninitialized_copy, std::ranges::uninitialized_copy_result

 

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Ranges library (C++20)

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External libraries

 

Algorithm library

Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Non-modifying sequence operations     Batch operations for_each for_each_n (C++17) Search operations all_ofany_ofnone_of (C++11)(C++11)(C++11) countcount_if mismatch equal findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n Modifying sequence operations Copy operations copycopy_if (C++11) copy_backward copy_n (C++11) move (C++11) move_backward (C++11) Swap operations swap iter_swap swap_ranges Transformation operations replacereplace_if transform replace_copyreplace_copy_if Generation operations fill fill_n generate generate_n Removing operations removeremove_if unique remove_copyremove_copy_if unique_copy Order-changing operations reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) shift_leftshift_right (C++20)(C++20) Sampling operations sample (C++17)	Sorting and related operations Partitioning operations partition partition_copy (C++11)     stable_partition is_partitioned (C++11)     partition_point (C++11) Sorting operations sort stable_sort partial_sort partial_sort_copy is_sorted (C++11) is_sorted_until (C++11) nth_element Binary search operations (on partitioned ranges) lower_bound upper_bound equal_range binary_search Set operations (on sorted ranges) includes set_union set_intersection          set_difference set_symmetric_difference Merge operations (on sorted ranges) merge inplace_merge Heap operations push_heap pop_heap make_heap sort_heap is_heap (C++11) is_heap_until (C++11) Minimum/maximum operations max min minmax (C++11) clamp (C++17) max_element min_element minmax_element (C++11) Lexicographical comparison operations lexicographical_compare lexicographical_compare_three_way (C++20) Permutation operations next_permutation prev_permutation is_permutation (C++11)	Execution policies (C++17) is_execution_policy (C++17) execution::seqexecution::parexecution::par_unseqexecution::unseq (C++17)(C++17)(C++17)(C++20) execution-policy (exposition only*)(C++26) execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_policyexecution::parallel_unsequenced (C++17)(C++17)(C++17)(C++20) Numeric operations iota (C++11) inner_product      reduce (C++17) accumulate adjacent_difference transform_reduce (C++17) partial_sum inclusive_scan (C++17)     exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17) Specialized <memory> algorithms Specialized <random> algorithms ranges::generate_random (C++26) C library qsort bsearch

 

Specialized <memory> algorithms

Helper templates (exposition only*) voidify deref-move (C++17) nothrow-input-iteratornothrow-forward-iteratornothrow-bidirectional-iteratornothrow-random-access-iterator (C++20)(C++20)(C++26)(C++26) nothrow-sentinel-fornothrow-sized-sentinel-for (C++20)(C++26) nothrow-input-rangenothrow-forward-rangenothrow-bidirectional-rangenothrow-random-access-rangenothrow-sized-random-access-range (C++20)(C++20)(C++26)(C++26)(C++26) Object (batch) construction construct_at (C++20) uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_copy_n (C++11) uninitialized_fill_n uninitialized_move_n (C++17) uninitialized_default_construct (C++17) uninitialized_default_construct_n (C++17)     uninitialized_value_construct (C++17) uninitialized_value_construct_n (C++17) ranges::construct_at (C++20) ranges::uninitialized_copy (C++20) ranges::uninitialized_fill (C++20) ranges::uninitialized_move (C++20) ranges::uninitialized_copy_n (C++20) ranges::uninitialized_fill_n (C++20) ranges::uninitialized_move_n (C++20) ranges::uninitialized_default_construct (C++20) ranges::uninitialized_default_construct_n (C++20) ranges::uninitialized_value_construct (C++20) ranges::uninitialized_value_construct_n (C++20) Object (batch) destruction destroy (C++17) destroy_n (C++17) destroy_at (C++17) ranges::destroy (C++20) ranges::destroy_n (C++20) ranges::destroy_at (C++20)

 

Defined in header <memory>
Call signature
template< std::input_iterator I, std::sentinel_for<I> S1, /*nothrow-forward-iterator*/ O, /*nothrow-sentinel-for*/<O> S2 > requires std::constructible_from<std::iter_value_t<O>, std::iter_reference_t<I>> uninitialized_copy_result<I, O> uninitialized_copy( I ifirst, S1 ilast, O ofirst, S2 olast );	(1)	(since C++20) (constexpr since C++26)
template< ranges::input_range IR, /*nothrow-forward-range*/ OR > requires std::constructible_from<ranges::range_value_t<OR>, ranges::range_reference_t<IR>> uninitialized_copy_result<ranges::borrowed_iterator_t<IR>, ranges::borrowed_iterator_t<OR>> uninitialized_copy( IR&& in_range, OR&& out_range );	(2)	(since C++20) (constexpr since C++26)
template< /*execution-policy*/ Ep, std::random_access_iterator I, std::sized_sentinel_for<I> S1, /*nothrow-random-access-iterator*/ O, /*nothrow-sized-sentinel-for*/<O> S2 > requires std::constructible_from<std::iter_value_t<O>, std::iter_reference_t<I>> uninitialized_copy_result<I, O> uninitialized_copy( Ep&& policy, I ifirst, S1 ilast, O ofirst, S2 olast );	(3)	(since C++26)
template< /*execution-policy*/ Ep, /*sized-random-access-range*/ IR, /*nothrow-sized-random-access-range*/ OR > requires std::constructible_from<ranges::range_value_t<OR>, ranges::range_reference_t<IR>> uninitialized_copy_result<ranges::borrowed_iterator_t<IR>, ranges::borrowed_iterator_t<OR>> uninitialized_copy( Ep&& policy, IR&& in_range, OR&& out_range );	(4)	(since C++26)
Helper types
template< class I, class O > using uninitialized_copy_result = ranges::in_out_result<I, O>;	(5)	(since C++20)

For the definition of /*execution-policy*/, see this page; for the definition of /*sized-random-access-range*/, see this page; for the definition of other exposition-only concepts, see this page.

1) Constructs elements in the destination range [ofirst, olast) from elements in the source range [ifirst, ilast) 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.

2) Same as (1), but uses in_range as the source range and out_range as the destination range.

3,4) Same as (1,2), but executed according to policy.

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.

Parameters

ifirst, ilast	-	the iterator-sentinel pair defining the source range of elements to copy from
in_range	-	the range of elements to copy from
ofirst, olast	-	the iterator-sentinel pair defining the destination range of elements
out_range	-	the destination range
policy	-	the execution policy to use

Return value

As described above.

Exceptions

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

3,4) During the execution process:

• If the temporary memory resources required for parallelization are not available, std::bad_alloc is thrown.
• If an uncaught exception is thrown while accessing objects via an algorithm argument, the behavior is determined by the execution policy (for standard policies, std::terminate is invoked).

Notes

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

Feature-test macro	Value	Std	Feature
__cpp_lib_parallel_algorithm	202506L	(C++26)	Parallel range algorithms
__cpp_lib_raw_memory_algorithms	202411L	(C++26)	constexpr for specialized <memory> algorithms, (1,2)

Possible implementation

struct uninitialized_copy_fn { template<std::input_iterator I, std::sentinel_for<I> S1, /*nothrow-forward-iterator*/ O, /*nothrow-sentinel-for*/<O> S2> requires std::constructible_from<std::iter_value_t<O>, std::iter_reference_t<I>> 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, /*nothrow-forward-range*/ OR> requires std::constructible_from<ranges::range_value_t<OR>, ranges::range_reference_t<IR>> constexpr ranges::uninitialized_copy_result<ranges::borrowed_iterator_t<IR>, ranges::borrowed_iterator_t<OR>> operator()(IR&& in_range, OR&& out_range) const { return (*this)(ranges::begin(in_range), ranges::end(in_range), ranges::begin(out_range), ranges::next(ranges::begin(out_range), ranges::end(out_range))); } template<ranges::forward_range IR, /*nothrow-forward-range*/ OR> requires std::constructible_from<ranges::range_value_t<OR>, ranges::range_reference_t<IR>> constexpr ranges::uninitialized_copy_result<ranges::borrowed_iterator_t<IR>, ranges::borrowed_iterator_t<OR>> operator()(IR&& in_range, OR&& out_range) const { return (*this)(ranges::begin(in_range), ranges::next(ranges::begin(in_range), ranges::end(in_range)), ranges::begin(out_range), ranges::next(ranges::begin(out_range), ranges::end(out_range))); } }; inline constexpr uninitialized_copy_fn uninitialized_copy{};

Example

Run this code

#include <cstdlib>
#include <iomanip>
#include <iostream>
#include <memory>
#include <string>

int main()
{
    const char* v[]{"This", "is", "an", "example"};
    
    if (const auto sz{std::size(v)};
        void* pbuf = std::aligned_alloc(alignof(std::string), sizeof(std::string) * sz))
    {
        try
        {
            auto first{static_cast<std::string*>(pbuf)};
            auto last{first + sz};
            std::ranges::uninitialized_copy(std::begin(v), std::end(v), first, last);
            
            std::cout << "{";
            for (auto it{first}; it != last; ++it)
                std::cout << (it == first ? "" : ", ") << std::quoted(*it);
            std::cout << "};\n";
            
            std::ranges::destroy(first, last);
        }
        catch (...)
        {
            std::cout << "uninitialized_copy exception\n";
        }
        std::free(pbuf);
    }
}

Output:

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

See also

ranges::uninitialized_copy_n (C++20)	copies a number of objects to an uninitialized area of memory (algorithm function object)
uninitialized_copy	copies a range of objects to an uninitialized area of memory (function template)