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# std::function::operator bool

From cppreference.com
< cpp‎ | utility‎ | functional‎ | function

explicit operator bool() const; |  | (since C++11)

Checks whether *this stores a callable function target, i.e. is not empty.

### [edit] Parameters

(none)

### [edit] Return value

true if *this stores a callable function target, false otherwise.

### [edit] Exceptions

`noexcept` specification:
noexcept

### [edit] Example

Run this code

    #include <functional>
    #include <iostream>

    typedef std::function<void(int)> SomeVoidFunc;

    class C {
      public:
        C(SomeVoidFunc void_func = nullptr)
            : void_func_(std::move(void_func))
        {
            if (!void_func_) {
                void_func_ = std::bind(&C::default_func, this, std::placeholders::_1);
            }
            void_func_(7);
        }

        void default_func(int i) { std::cout << i << '\n'; };

      private:
        SomeVoidFunc void_func_;
    };

    void user_func(int i)
    {
        std::cout << (i + 1) << '\n';
    }

    int main()
    {
        C c1;
        C c2(user_func);
    }

Output:

    7
    8

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