#include<iostream>
#include<cmath>
  
template<typename F> double integrate(F f,double  min,double max,double ds) {
  double integral=.0;
  for(double x=min;x<max;x+=ds) {
    integral+=f(x);
  }
  return integral*ds;
};


class sina {
  double _a;
public:
  sina(double a): _a(a) {};
  double operator()(double x) {return sin(_a*x);}
};

main() {

  std::cout<<  ::integrate(sin,0,3.1415926,0.01)<<std::endl;

  std::cout<<  ::integrate(sina(0),0,3.1415926,0.01)<<std::endl;
  std::cout<<  ::integrate(sina(1),0,3.1415926,0.01)<<std::endl;
  std::cout<<  ::integrate(sina(2),0,3.1415926,0.01)<<std::endl;
}