main.cpp

#import "planet.h"

#include <iostream>

using namespace std;

const double G = 1;
const double m_sun = 1;
const double m_earth = 1;

void leapfrog_step(std::vector<Particle>& particles, double dt) {
  for (vector<Particle>::iterator p = particles.begin(); p != particles.end(); ++p) {
  }
}

int main (int argc, char * const argv[]) {
  Simulator sim(leapfrog_step);
}

planet.cpp

#include "planet.h"

#include <cmath>
#include <iostream>

using namespace std;

xyvect::xyvect(double x0, double y0): x(x0), y(y0) {}

double xyvect::normsq() { return x*x + y*y; }
double xyvect::norm() { return sqrt(normsq()); }
double xyvect::ang() { return atan2(y,x); }

Particle::Particle(double mass, xyvect x0, xyvect v0): m(mass), x(x0), v(v0) {}

double Particle::mass() { return m; }

Simulator::Simulator(void(*stepFn)(std::vector<Particle>&, double)): step(stepFn) {}

void Simulator::add(Particle &p) {
  particles.push_back(p);
}

int Simulator::run() {
  for (vector<Particle>::iterator p = particles.begin(); p != particles.end(); ++p) {
    cout << (*p).mass() << endl;
  }
  return 0;
}
  
// void leapfrog_step(std::vector<Particle>& particles, double dt) {
//   for (vector<Particle>::iterator p = v.begin(); p != v.end(); ++p) {
//     *p.x_inc(0.5*dt);
//     *p.a_calc();
//     *p.v_inc(dt);
//     *p.x_inc(0.5*dt);
//     *p.t_inc(dt);
//   }
// }
// 
// void euler_step(std::vector<Particle>& particles, double dt) {
//   for (vector<Particle>::iterator p = v.begin(); p != v.end(); ++p) {
//     *p.a_calc();
//     *p.x_inc(dt);
//     *p.v_inc(dt);
//     *p.t_inc(dt);
//   }
// }
// 

planet.h

#include <vector>

#ifndef PLANET_H
#define PLANET_H

class xyvect {
  public:
    xyvect(double xx, double yy);
    
    double normsq();
    double norm();
    double ang();
    
  private:
    double x, y;
};

class Particle {
  public:
    Particle(double mass, xyvect x0, xyvect v0);
    
    double mass();

  private:
    double m;
    xyvect x;
    xyvect v;
};

class Simulator {
  public:
    Simulator(void(*step)(std::vector<Particle>&, double));

    void add(Particle &p);
    int run();
    
  private:
    std::vector<Particle> particles;
    void(*step)(std::vector<Particle>&, double);
};

void leapfrog_step(std::vector<Particle>& particles, double dt)

#endif