#define MAXX 100
#define MAXY 100
#define KMOLLA 0.1
#define DT .02
#define G 5
#include <iostream>
#include <cmath>

using namespace std;

class Palla{
 public:
  Palla(float x, float y, float m);
  void setVel(float vx, float vy);
  void evolvi(Palla altraPalla);

  float x(){
    return xPos;
  }
  float y(){
    return yPos;
  }
  float vx(){
    return velX;
  }
  float vy(){
    return velY;
  }
  
 private:
  float dist(Palla);
  float cosX(Palla);
  float cosY(Palla);
  
  float xPos, yPos, massa;
  float velX, velY;
};

Palla::Palla(float x, float y, float m){
  xPos = x;
  yPos = y;
  massa = m;
  velX=0;
  velY=0;
}


float Palla::dist(Palla p){
  return (sqrt(
	       (xPos-p.x())*(xPos-p.x())+
	       (xPos-p.y())*(xPos-p.y())));
}


float Palla::cosX(Palla p){
  return (xPos-p.x())/dist(p);
}
float Palla::cosY(Palla p){
  return (yPos-p.y())/dist(p);
}


void Palla::evolvi(Palla p){
  float d = dist(p);
  float ax = -(d-5)/massa*KMOLLA*cosX(p); 
  float ay = -(d-5)/massa*KMOLLA*cosY(p)-G;
  
  cout <<" ACCEL "<<ax<<" " <<ay<<endl;

  velX += ax*DT; 
  velY += ay*DT; 
  
  xPos+=velX*DT;
  yPos+=velY*DT;
  //
  // controlla il bordo
  //
  if (xPos <= 0) {
    xPos=0;
    velX= -velX;
  }
  if (xPos >= MAXX) {
    xPos=MAXX;
    velX= -velX;
  }
  if (yPos <= 0) {
    yPos=0;
    velY= -velY;
  }
  if (yPos >= MAXY) {
    yPos=MAXY;
    velY= -velY;
  }
}

int main(){
  Palla palla1 (10,10,2);
  Palla palla2 (20,5,9);
  
  while(1){
    palla1.evolvi(palla2);
    palla2.evolvi(palla1);    
    cout <<" PALLA 1 "<<palla1.x()<<" "<< palla1.y()<<" =V= "<<palla1.vx()<<" "<< palla1.vy()<<endl;
    cout <<" PALLA 2 "<<palla2.x()<<" "<< palla2.y()<<" =V= "<<palla2.vx()<<" "<< palla2.vy()<<endl;
  }
}