View difference between Paste ID: dZVmTWXz and jiCnrR94

 #include <iostream>
 using namespace std;
 
 class vec {
 friend class arr_vec;
 private: double x, y, z;
 public: friend vec operator+ (vec, vec);
 friend vec operator* (vec, double);
 friend vec operator* (double, vec);
 friend vec toVec(double x, double y, double z);
 };
 
 vec toVec (double x, double y, double z) {
 vec v;
 v.x=x;
 v.y=y;
 v.z=z;
 return v;
 }
 vec operator+ (vec c, vec d) {
 return toVec(c.x+d.x, c.y+d.y, c.z+d.z);}
 
 vec operator* (vec c, double d) {
 return toVec(c.x*d, c.y*d, c.z*d);}
 
 vec operator* (double c, vec d) {
 return toVec(c*d.x, c*d.y, c*d.z);}
 
 class arr_vec {
 private: double *x, *y, *z;
 int n;
 public: arr_vec(int);
 ~arr_vec();
 void set(int, vec);
 vec operator[] (int) const;
 void operator=(const arr_vec&);
 friend arr_vec operator+ (const arr_vec&, const arr_vec&);
 friend arr_vec operator* (double, const arr_vec&);
 friend arr_vec operator* (const arr_vec&, double);
 void show();
 };
 void arr_vec::operator =(const arr_vec& A) {
     n=A.n;
     x= new double [n];
     y=new double[n];
     z=new double [n];
     for(int i=0; i<n; i++) {x[i]=A.x[i]; y[i]=A.y[i]; z[i]=A.z[i];}
 }
 
 arr_vec::arr_vec(int N) {
 n=N;
 x=new double[n];
 y=new double[n];
 z=new double[n];
 for(int i=0; i<n; i++) {x[i]=y[i]=z[i]=1;}
 }
 arr_vec::~arr_vec() {
 delete[]x;
 delete[]y;
 delete[]z;
 }
 void arr_vec::set(int N, vec vvv) {
 if (n<N) return;
 x[N]=vvv.x;
 y[N]=vvv.y;
 z[N]=vvv.z;
 }
 vec arr_vec::operator [](int N) const {
 return toVec(x[N], y[N], z[N]);
 }
 arr_vec operator+ (const arr_vec& c, const arr_vec& d) {
 arr_vec *e;
 e=new arr_vec(c.n);
 for(int i=0; i<e->n; i++) e->set(i, c[i]+d[i]);
 return *e;
 }
 arr_vec operator* (double c, const arr_vec& d) {
 arr_vec *e;
 e=new arr_vec(d.n);
 for (int i=0; i<e->n; i++) e->set(i, c*d[i]);
 return *e;
 }
 arr_vec operator* (const arr_vec& c, double d) {
 arr_vec *e;
 e=new arr_vec(c.n);
 for (int i=0; i<e->n; i++) e->set(i, c[i]*d);
 return *e;
 }
 void arr_vec::show() {
 cout<<endl<<"X: ";
 for(int i=0; i<n; i++) cout<<x[i]<<"\t";
 cout<<endl<<"Y: ";
 for(int i=0; i<n; i++) cout<<y[i]<<"\t";
 cout<<endl<<"Z: ";
 for(int i=0; i<n; i++) cout<<z[i]<<"\t";
 cout<<endl;
 }
 
 int main() {
 arr_vec c(2), d(2);
 vec e, f;
 e=toVec(1,2,3);
 f=toVec(4,5,6);
 c.set(0, e);
 c.show();
 c=c+c;
 c.show();
 }