Difference between revisions of "cpp/memory/ranges/destroy"
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inline constexpr destroy_fn destroy{}; | inline constexpr destroy_fn destroy{}; | ||
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| + | ===Example=== | ||
| + | {{cpp/memory/destroy example|ranges::destroy}} | ||
===See also=== | ===See also=== | ||
Revision as of 21:34, 31 August 2020
| Defined in header <memory>
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| Call signature |
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| template< no-throw-input-iterator I, no-throw-sentinel-for<I> S > requires std::destructible<std::iter_value_t<I>> |
(1) | (since C++20) |
| template< no-throw-input-range R > requires std::destructible<ranges::range_value_t<R>> |
(2) | (since C++20) |
1) Destroys the objects in the range
[first, last), as if by
for (; first != last; ++first) std::ranges::destroy_at(std::addressof(*first)); return first;
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 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.
Contents |
Parameters
| first, last | - | iterator-sentinel pair denoting the range of elements to destroy |
| r | - | the range to destroy |
Return value
An iterator compares equal to last.
Complexity
Linear in the distance between first and last.
Possible implementation
struct destroy_fn { template</*no-throw-input-iterator*/ I, /*no-throw-sentinel-for*/<I> S> requires std::destructible<std::iter_value_t<I>> constexpr I operator()(I first, S last) noexcept { for (; first != last; ++first) std::ranges::destroy_at(std::addressof(*first)); return first; } template</*no-throw-input-range*/ R> requires std::destructible<std::ranges::range_value_t<R>> constexpr std::ranges::borrowed_iterator_t<R> operator()(R&& r) noexcept { return operator()(std::ranges::begin(r), std::ranges::end(r)); } }; inline constexpr destroy_fn destroy{}; |
Example
The following example demonstrates how to use ranges::destroy to destroy a contiguous sequence of elements.
Run this code
#include <iostream> #include <memory> #include <new> 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 construct objects auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer)); std::ranges::destroy(ptr, ptr + 8); }
Output:
0 destructed 1 destructed 2 destructed 3 destructed 4 destructed 5 destructed 6 destructed 7 destructed
See also
| (C++20) |
destroys a number of objects in a range (niebloid) |
| (C++20) |
destroys an object at a given address (niebloid) |
| (C++17) |
destroys a range of objects (function template) |
