std::shared_future::valid(3)

💅 NAME 💅

Okay so bestie, welcome to std::shared_future::valid(3), straight from the C++ Standard Libary manual — yes, that's the spelling in the header, and we are respecting the typo 😭. The NAME is literally std::shared_future::valid - std::shared_future::valid; it's giving "I contain multitudes" energy 💖.

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✨ Synopsis ✨

bool valid() const noexcept;  (since C++11)

Checks if the future refers to a shared state 🫶. This is the case only for futures that were not default-constructed or moved from — no cap.

Unlike std::future, std::shared_future's shared state is not invalidated when get() is called. The way that survives get() is lowkey iconic 💅.

🚨 Serious bestie warning: the behavior is undefined if any member function other than the destructor, the copy-assignment operator, the move-assignment operator, or valid is called on a shared_future that does not refer to shared state. Implementations are encouraged to throw std::future_error indicating no_state in this case — but that's encouragement, not a guarantee. Do not test this. It is not the vibe. 💀

It is valid to move or copy from a shared_future object for which valid() is false — that part is safe and slay 🎀.

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🎀 Parameters 🎀

(none) — literally no parameters. Zero. Zilch. Not even a little guy 🙈.

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🌸 Return value 🌸

true if *this refers to a shared state, otherwise false. That's it, that's the return value, and it understood the assignment ✨.

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🦋 Example 🦋

It says // Run this code, then it does this:

#include <future>
#include <iostream>

int main()
{
    std::promise<void> p;
    std::shared_future<void> f = p.get_future();

    std::cout << std::boolalpha;

    std::cout << f.valid() << '\n';
    p.set_value();
    std::cout << f.valid() << '\n';
    f.get();
    std::cout << f.valid() << '\n';
}

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🍓 Output 🍓

true
true
true

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👑 See also 👑

• wait — waits for the result to become available (public member function). That's the only see-also, and it's carrying the whole reference section on its back 💪.

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That's the whole page, bestie. It came from http://cppreference.com, dated 2024.06.10, and it's std::shared_future::valid(3) — bye, love u, mwah 💋💖