c++ functional interface

gauge.cpp

#include <functional>
#include <iostream>

class Foo {
public:
	Foo(std::function<double()> gauge) {
		this->_gauge = gauge;
	}

	void invoke() {
		double g = _gauge();

		std::cout << "calling gauge returned: " << g << std::endl;
	}

	std::function<double()> _gauge;
};

void call_it(Foo *foo) {
	foo->invoke();
}

int main() {
	double val = 4.5;
	class Foo *f = new Foo([&val] {
		    std::cout << "calling function " << std::endl;
		    return val;
	    });

	call_it(f);
	return 0;
}