std::ranges::destroy
From cppreference.com
| 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>> constexpr I destroy( I first, S last ) noexcept; |
(1) | (since C++20) |
template< no-throw-input-range R > requires std::destructible<ranges::range_value_t<R>> constexpr ranges::borrowed_iterator_t<R> destroy( R&& r ) noexcept; |
(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 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
|
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) const 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) const noexcept
{
return operator()(std::ranges::begin(r), std::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) |