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std::ranges::destroy_n(3) C++ Standard Libary std::ranges::destroy_n(3) NAME std::ranges::destroy_n - std::ranges::destroy_n Synopsis Defined in header <memory> Call signature template< no-throw-input-iterator I > requires std::destructible<std::iter_value_t<I>> (since C++20) constexpr I destroy_n( I first, std::iter_difference_t<I> n ) noexcept; Destroys the n objects in the range starting at first, equivalent to return std::ranges::destroy(std::counted_iterator(first, n), std::de- fault_sentinel).base(); The function-like entities described on this page are niebloids, that is: * Explicit template argument lists may not be specified when call- ing any of them. * None of them is visible to argument-dependent lookup. * When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup. In practice, they may be implemented as function objects, or with special compiler extensions. Parameters first - the beginning of the range of elements to destroy n - the number of elements to destroy Return value The end of the range of objects that has been destroyed. Complexity Linear in n. Possible implementation struct destroy_n_fn { template<no-throw-input-iterator I> requires std::destructible<std::iter_value_t<I>> constexpr I operator()(I first, std::iter_difference_t<I> n) const noexcept { for (; n != 0; (void)++first, --n) std::ranges::destroy_at(std::addressof(*first)); return first; } }; inline constexpr destroy_n_fn destroy_n{}; Example The following example demonstrates how to use ranges::destroy_n to destroy a contiguous sequence of elements. // Run this code #include <memory> #include <new> #include <iostream> struct Tracer { int value; ~Tracer() { std::cout << value << " destructed\n"; } }; int main() { alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8]; for (int i = 0; i < 8; ++i) new(buffer + sizeof(Tracer) * i) Tracer{i}; //manually con- struct objects auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer)); std::ranges::destroy_n(ptr, 8); } Output: 0 destructed 1 destructed 2 destructed 3 destructed 4 destructed 5 destructed 6 destructed 7 destructed See also ranges::destroy_at destroys an object at a given address (C++20) (niebloid) ranges::destroy destroys a range of objects (C++20) (niebloid) destroy_n destroys a number of objects in a range (C++17) (function template) http://cppreference.com 2022.07.31 std::ranges::destroy_n(3)
NAME | Synopsis | Parameters | Return value | Complexity | Possible implementation | Example | Output: | See also
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