How to initialize std::vector of function pointers to operator overloads?

Question

I'm trying to make a std::vector out of pointers to four operator overloading member functions. What's wrong with this:

struct Fractal
{   int dividee;
    int divisor;

    Fractal operator +(Fractal other)
    {   [not important]
    }

    Fractal operator -(Fractal other)
    {   [not important]
    }

    Fractal operator *(Fractal other)
    {   [not important]
    }

    Fractal operator /(Fractal other)
    {   [not important]
    }
};

int main()
{   Fractal fractal = Fractal{3, 10};

    typedef Fractal(*fractalOperator)(Fractal, Fractal);
    std::vector<fractalOperator> ops =
    {   &Fractal::operator +,
        &Fractal::operator -,
        &Fractal::operator *,
        &Fractal::operator /
    };
}

Compiler says

error: could not convert '{&Fractal::operator+, &Fractal::operator-, &Fractal::operator*, &Fractal::operator/}' from '<brace-enclosed initializer list>' to 'std::vector<Fractal (*)(Fractal, Fractal)>'
 };

Which is not very helpful. What's the correct way? I'm using c++14.

Answer 1

Your typedef is for a pointer to function which takes two Fractals and returns a Fractal. What you want is a pointer to member function, which has a different syntax.

typedef Fractal(Fractal::*fractalOperator)(Fractal);

Or, with a using alias, which I find easier to read

using fractalOperator = Fractal(Fractal::*)(Fractal);