std::ranges::destroy
From cppreference.com
| Defined in header <memory>
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| Call signature |
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template< /*nothrow-input-iterator*/ I, /*nothrow-sentinel-for*/<I> S >
requires std::destructible<std::iter_value_t<I>>
constexpr I destroy( I first, S last ) noexcept;
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(1) | (since C++20) |
template< /*nothrow-input-range*/ R >
requires std::destructible<ranges::range_value_t<R>>
constexpr ranges::borrowed_iterator_t<R> destroy( R&& r ) noexcept;
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(2) | (since C++20) |
template< /*execution-policy*/ Ep, /*nothrow-random-access-iterator*/ I,
/*nothrow-sized-sentinel-for*/<I> S >
requires std::destructible<std::iter_value_t<I>>
I destroy( Ep&& policy, I first, S last );
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(3) | (since C++26) |
template< /*execution-policy*/ Ep, /*nothrow-sized-random-access-range*/ R >
requires std::destructible<ranges::range_value_t<R>>
ranges::borrowed_iterator_t<R> destroy( Ep&& policy, R&& r );
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(4) | (since C++26) |
For the definition of /*execution-policy*/, see this page; for the definition of other exposition-only concepts, see this page.
1) Destroys elements in the target 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 target 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
| first, last | - | the iterator-sentinel pair defining the range of elements to destroy |
| r | - | the range to destroy |
| policy | - | the execution policy to use |
Return value
As described above.
Exceptions
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
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_parallel_algorithm |
202506L |
(C++26) | Parallel range algorithms |
Possible implementation
struct destroy_fn
{
template</*nothrow-input-iterator*/ I, /*nothrow-sentinel-for*/<I> S>
requires std::destructible<std::iter_value_t<I>>
constexpr I operator()(I first, S last) const noexcept
{
for (; first != last; ++first)
ranges::destroy_at(std::addressof(*first));
return first;
}
template</*nothrow-input-range*/ R>
requires std::destructible<ranges::range_value_t<R>>
constexpr ranges::borrowed_iterator_t<R> operator()(R&& r) const noexcept
{
return (*this)(ranges::begin(r), ranges::end(r));
}
template</*nothrow-forward-range*/ R>
requires std::destructible<ranges::range_value_t<R>>
constexpr ranges::borrowed_iterator_t<R> operator()(R&& r) const noexcept
{
return (*this)(ranges::begin(r),
ranges::next(ranges::begin(r), ranges::end(r)));
}
};
inline constexpr destroy_fn destroy{};
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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 (algorithm function object) |
(C++20) |
destroys an object at a given address (algorithm function object) |
(C++17) |
destroys a range of objects (function template) |