# std::optional<T>::operator bool, std::optional<T>::has_value

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< cpp‎ | utility‎ | optional

constexpr explicit operator bool() const noexcept; |  | (since C++17)
constexpr bool has_value() const noexcept; |  | (since C++17)

Checks whether *this contains a value.

### Parameters

(none)

### Return value

true if *this contains a value, false if *this does not contain a value.

### Example

Run this code

    #include <optional>
    #include <iostream>

    int main()
    {
        std::cout << std::boolalpha;

        std::optional<int> opt;
        std::cout << opt.has_value() << '\n';

        opt = 43;
        if (opt)
            std::cout << "value set to " << opt.value() << '\n';
        else
            std::cout << "value not set\n";

        opt.reset();
        if (opt.has_value())
            std::cout << "value still set to " << opt.value() << '\n';
        else
            std::cout << "value no longer set\n";
    }

Output:

    false
    value set to 43
    value no longer set

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