# std::ranges::destroy

From cppreference.com
< cpp‎ | memory

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 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 | - | 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) 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{};

### 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

ranges::destroy_n (C++20) | destroys a number of objects in a range (algorithm function object)
ranges::destroy_at (C++20) | destroys an object at a given address (algorithm function object)
destroy (C++17) | destroys a range of objects (function template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/memory/ranges/destroy&oldid=154776"