Class member function pointer that uses another class member

Question

I'm trying to make a code that find the numerical derivation of a function. I also have a polynomial class described as follows:

    class polynomial
    {
    public:
        polynomial(Vector, int);
        polynomial();
        ~polynomial();

        double returnValue(double);
        void print();

    private:
        int Degree;
        Vector Coeficients;
    };

my numerical derivation have the following prototype:

 double numericalDerivation( double (*F) (double), double x);

I want to pass the returnValue method into the numericalDerivation, is that possible?

No. `returnValue` isn't a function, i.e. you cannot *call* it. Search this site for hundreds of duplicates on how to deal with member function pointers. — Kerrek SB, Feb 19 '13 at 01:44
Actually, `returnValue` is a function, but a member function. `numericalDerivation` expects a function pointer, not a member function pointer (that would be a different type). — jogojapan, Feb 19 '13 at 01:49

Andy Prowl · Accepted Answer · 2013-02-19T01:55:23.263

0

Yes, it is possible, but don't forget it is a member function: you won't be able to call it without having a (pointer to) an object of type polynomial on which to invoke it.

Here is how the signature of your function should look like:

double numericalDerivation(double (polynomial::*F)(double), polynomial* p, double x)
{
    ...
    (p->*F)(x);
    ...
}

Here is how you would invoke it:

double d = ...;
polynomial p;
numericalDerivation(&polynomial::returnValue, &p, d);

Alternatively, you could use an std::function<> object as a parameter of your function, and let std::bind() take care of binding the object to the member function:

#include <functional>

double numericalDerivation(std::function<double(double)> f, double x)
{
    ...
    f(x);
    ...
}

...

double d = ...;
polynomial p;
numericalDerivation(std::bind(&polynomial::returnValue, p, std::placeholders::_1), d);

edited Feb 19 '13 at 01:55

answered Feb 19 '13 at 01:49

Andy Prowl

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Thank for your solution, the first solution works also if I use overloads, I tried the second solution and got the following error: term does not evaluate to a function taking 1 arguments, it works now, thanks !! – Lucas Da Rocha Souza Feb 19 '13 at 02:00
@LucasDaRochaSouza: Wait, is it working or not? – Andy Prowl Feb 19 '13 at 02:06
Sorry for the confusion, got it working now, thanks. – Lucas Da Rocha Souza Feb 19 '13 at 02:07
@LucasDaRochaSouza: Ok. Please consider accepting or at least upvoting this answer if it helped. – Andy Prowl Feb 19 '13 at 02:08
Btw, do you have any suggestions on where I can learn more about other then reference web sites? – Lucas Da Rocha Souza Feb 19 '13 at 02:11
@LucasDaRochaSouza: Online tutorials are a good starting point I think. For instance, if you type "std::function tutorial" you can get to links like [this one](http://www.dreamincode.net/forums/topic/264061-c11-fun-with-functions/) – Andy Prowl Feb 19 '13 at 02:13

Class member function pointer that uses another class member

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