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std::ranges::destroy

From cppreference.com
< cpp‎ | memory
 
 
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Defined in header <memory>
Call signature
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 niebloids, that is:

In practice, they may be implemented as function objects, or with special compiler extensions.

Contents

[edit] Parameters

first, last - iterator-sentinel pair denoting the range of elements to destroy
r - the range to destroy

[edit] Return value

An iterator compares equal to last.

[edit] Complexity

Linear in the distance between first and last.

[edit] 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{};

[edit] Example

The following example demonstrates how to use ranges::destroy to destroy a contiguous sequence of elements.

#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 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

[edit] See also

destroys a number of objects in a range
(niebloid) [edit]
destroys an object at a given address
(niebloid) [edit]
(C++17)
destroys a range of objects
(function template) [edit]