[Help-gsl] Interpolated Values as function return

[Klaus Huthmacher]

Dear Ladies and Gentlemen,

finally I succeeded in writing a (hopefully modern) wrapper around the 
interpolated data set and pass it to the GSL integration method.

Maybe it helps others.

Kind regards and have a nice weekend,

    Klaus Huthmacher.
#include <gsl/gsl_integration.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_spline.h>
#include <iostream>
#include <memory>
#include <vector>

class parameters
{
	public:
		parameters();
		double get(double);

	private:
		std::vector<double> x, y;
		std::unique_ptr<gsl_interp_accel,void(*)(gsl_interp_accel*)> acc;
		std::unique_ptr<gsl_spline,void(*)(gsl_spline*)> spline;
};
/*
---{}--- constructor ---{}---
*/
parameters::parameters():
x({{0.0,1.0,2.0}}),y({{0.0,1.0,2.0}}),
acc(gsl_interp_accel_alloc(),gsl_interp_accel_free),
spline(gsl_spline_alloc(gsl_interp_cspline,x.size()),gsl_spline_free)
{
	gsl_spline_init(spline.get(),x.data(),y.data(),x.size());
}
/*
---{}--- parameters::get ---{}---
*/
auto parameters::get(double x) -> double
{
	return gsl_spline_eval(spline.get(),x,acc.get());
}
/*
---{}--- gsl function ---{}---
*/
double function(double x, void* ptr)
{
	parameters* params = static_cast<parameters*>(ptr);
	return params->get(x);
}

int main()
{
	parameters params;

	gsl_function F;

	F.function = &function;
	F.params = &params;

	double result, error;

	std::unique_ptr<gsl_integration_workspace,void(*)(gsl_integration_workspace*)>
		w(gsl_integration_workspace_alloc(1000),gsl_integration_workspace_free);

	gsl_integration_qags(&F,0,2,0,1.0e-7,1000,w.get(),&result,&error);

	std::cout << result << std::endl;

	return 0;
}
<<attachment: huthmacher.vcf>>