CODEWITHSUNDEEP
c++operator-keyword
Nessya Nakache
Nessya Nakache

Reputation: 11

a pointer to function within a operator

for homework, I need to write a program in cpp with a class composed of an array of pointer to function and operators. I need to create an operator + so as when in the main, this would happen:

int main()
{
int SIZE = 5;
ptrF* arrPtrF = new ptrF[SIZE];
arrPtrF[0] = add;
arrPtrF[1] = sub;
arrPtrF[2] = mult;
arrPtrF[3] = div1;
arrPtrF[4] = pow;
Delegate D1(arrPtrF, SIZE)
cout<< D1[0](6, 7) + D1[0](1, 2)<<endl; 
}

the outcome is 15

I am finding difficulty with writing the operator+ ( which in this case need to take take a object parameter)

at first i tried this:

Delegate Delegate:: operator + (const Delegate& b)
{
Delegate tmp;

tmp.m_ptrF[i] = m_ptrF[i] + b.m_ptrF[i];

return tmp;
}

but it gave me an error about the i and b.m_ptrF->initialized i and something about an enum type.

then i tried this:

int Delegate:: operator + (const Delegate& b)
{
int tmp;
int i, x,y;

    tmp = m_ptrF[i](x, y) + b.m_ptrF[i](x, y);

return tmp;
}

but it gives me an error->initialized x,y,i knowing that i is index and x,y the parameters of the pointer to function.

what can i do to make it work?

Upvotes: 0

Views: 76

Answers (1)

john
john

Reputation: 87959

It looks like D1[0](6, 7) is supposed to perform 6 + 7 returning an int and D1[0](1, 2) is supposed to perform 1 + 2 also returning an int. So the addition in D1[0](6, 7) + D1[0](1, 2) is just a regular int addition.

So in other words you are not supposed to be overloading Delegate::operator+ instead you are supposed to writing something like this

XXX Delegate::operator[](int i) const
{
    ...
}

where XXX is a function like type that will perform the addition on the later parameters.

So XXX will be something like

class XXX
{
public:
    int operator()(int x, int y) const
    {
        ...
    }
    ...
};

But XXX will have to perform addition, or substraction or whatever, as appropriate.

So the expression D1[0](6, 7) becomes temp(6,7) where temp is an object of the XXX type above.

At least that's my best interpretation. It's clear that you have misunderstood your requirements.

Upvotes: 1

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