std::ranges::destroy(3)

💖 std::ranges::destroy 💖

okay so this is std::ranges::destroy(3) from the C++ Standard Libary manual — manual name folded in near the top, spelling exactly the way the header gives it. bestie, we are destroying objects in a range, and the range-vibes are immaculate ✨

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✨ NAME ✨

std::ranges::destroy — std::ranges::destroy

(yes, the NAME section is literally serving the same name twice, and honestly? iconic 💅)

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📞 Synopsis 📞

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>>
(1) (since C++20)

constexpr I destroy( I first, S last ) noexcept;

template< no-throw-input-range R >
    requires std::destructible<ranges::range_value_t<R>>
(2) (since C++20)

constexpr ranges::borrowed_iterator_t<R> destroy( R&& r )
noexcept;

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.

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🧚 Parameters 🧚

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

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🎀 Return value 🎀

An iterator compares equal to last.

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🌀 Complexity 🌀

Linear in the distance between first and last.

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🛠️ 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.

The original page has this little button text: // 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);
}

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🖨️ Output 🖨️

0 destructed
1 destructed
2 destructed
3 destructed
4 destructed
5 destructed
6 destructed
7 destructed

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👀 See also 👀

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

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mwah 💋 — footer tea, folded into a cute sign-off: source http://cppreference.com, version/date 2024.06.10, page std::ranges::destroy(3). periodt 🫶