std::inner_product in class template

[kon]

Hi!

I encounter a problem when I tried to use inner product inside the class (I need to subtract the absolute values of two vectors). I cannot pass my own binaryOperaton function as an argument to inner_product(...) when this binaryOperation is defined inside the class.

My class look like this:

template <int dim>
class Convergence
{
    public:
// ...other stuff ...
    double myaccumulator(double x, double y)
    {
	return x + std::abs(y);
    }

    double myproduct(    double x, double y)
    {
	return x - y;
    }

    double calculate_differences(std::vector<double> vect1,
                                 std::vector<double> vect2)
    {
      return std::inner_product(std::begin(vect1),
                                std::end(vect1),
                                std::begin(vect2),
                                0,
                                myaccumulator,
                                myproduct);
    }
// ... other stuff ...
}

The following error appears:
error: invalid use of non-static member function ‘double Convergence<dim>::myaccumulator(double, double) [with int dim = 2]’

Can someone tell me what is incorrect in this implementation?

[Ganado]

Declare the functions myaccumulator and myproduct as static since they don't rely on class data.

[kon]

Yes, that works! Thank you very much!