Hi all,

Can someone please provide an example of how to create a functor that can have two variables being passed into it?

For example:

I need to create a functor that has two variables, Val1 and Val2.

The resulting equation is Val1+Val2*x

That equation needs to be used by qtrap.

The end result is the integral of the simple linear function.

Thanks
Matt

...functor that can have two variables being passed into it?...
Matt


// Driver for routine qtrap
//
// davekw7x

// Use whatever path you need...
#include "../code/nr3.h"
#include "../code/quadrature.h"


// Test function to integrate is a functor.
//
struct Ftor
{
// Parameters will be set by constructor
Doub a, b;

// Constructor
Ftor(Doub aa, Doub bb): a(aa), b(bb){}

// Overloaded () operator that will be used by qtrap.
// Must have this footprint: a function that
// returns a double, and has a single parameter that
// is a const double.
// (Could use standard C++ "double" for data types.)
//
Doub operator ()(const Doub x) const
{
return a*x + b;
}
};

int main()
{

// Set up limits of integration to feed to qtrap
Doub xmin = -1.0, xmax = 1.0;

// Set up parameters for the functor so that qtrap
// can integrate.
//
Doub a = 2.0, b = 7.0;
Ftor f(a, b);

Doub value = qtrap(f, xmin, xmax);
cout << "From qtrap, for a = " << a << " and b = " << b << ":" << endl
<< "The integral of a*x+b as x goes from "
<< xmin << " to " << xmax
<< " is " << scientific << value << endl;

return 0;
}


Output:

From qtrap, for a = 2 and b = 7:
The integral of a*x+b as x goes from -1 to 1 is 1.400000e+01


Regards,

Dave

Dave,

Thanks.

I figured it out, not long after I posted this question. I had simple error in the way I laid the struct out. I just hadn't had a chance to log in to the forum until now.

Thanks
Matt