ConversionOperator, C++ (gcc)

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//g++  7.4.0
//conversion operator: converting a Point class object into a Vector class object
//this code is created by Rezaul Hoque on September 15,2021
//note: codes shared by Rezaul Hoque on rextester are not for sale; they are created and shared to facilitate the algorithm learning process; many like Hoque use this platform to practice programming ;Rezaul hopes his contribution helps others to fine tune their learning;

#include <iostream>
#include <cmath>
class Vector {

friend std::ostream& operator<<(std::ostream &, const Vector &);//stream extraction operator
friend std::istream& operator>>(std::istream &, Vector &);//stream insertion operator

friend Vector operator+(const Vector &, const Vector&);//binary addition operator
friend Vector operator-(const Vector &, const Vector&);//binary subtraction operator
public:
Vector (int ,double );//default constructor
Vector(double,double,double);
Vector (const Vector &);//copy constructor
~Vector();//destructor
const Vector & operator=(const Vector &);//assignment operator
double& operator[](int) const;//subscript operator
Vector norm();

int size;
double a,b,c;
double * data;
};

std::ostream& operator<<(std::ostream& ostr,const Vector& v)
{
int l;
ostr<<"( ";
for(l=0;l<v.size-1;l++){
ostr<<v[l]<<",";
if((l+1)%8 == 0)  std::cout<<"\n"; }
return ostr<<v[l]<<")\n";
}
std::istream& operator>>(std::istream& istr,const Vector& v)
{
for(int l=0;l<=v.size-1;l++)
{
std::cout<<l<<":";
istr>>v[l];
}
return istr;
}
Vector::Vector(int sz=1,double t=0.0): size(sz)
{
data = new double[size];
for(int l=0;l<size;l++)
data[l]=t;
}
Vector::Vector(double t=0.0,double u=0.0,double v=0.0)
{
a=t;
b=u;
c=v;
}
Vector:: Vector(const Vector & v): size(v.size)
{ 
data = new double[v.size];
for(int l=0;l<v.size;l++)
data[l]=v.data[l];
}
Vector::~Vector()
{
delete [] data;
data = NULL;
size=0;
}

const Vector& Vector::operator=(const Vector & v)
{
if(&v != this)
  {
 delete [] data;
size = v.size;
data = new double[size];
for(int l=0;l<size;l++)
data[l]=v.data[l];
}
return *this;
}

double& Vector:: operator[](int I) const
{
return data[I];
}
Vector operator+(const Vector & v,const Vector& w)
{  Vector z(4,0.0);

for(int l=0;l<z.size;l++){
z.data[l] = v.data[l] + w.data[l];}
return z;
}
Vector operator-(const Vector & v,const Vector& w)
{  Vector z(4,0.0);

for(int l=0;l<z.size;l++){
z.data[l] = v.data[l] - w.data[l];}
return z;
}

Vector Vector:: norm()
{
Vector z(4);
for(int l=0; l<size; l++)
z.data[l] +=sqrt(data[l]*data[l]);
return z;
}
class Point{
friend std::ostream& operator<<(std::ostream&,const Point&);
friend std::istream& operator>>(std::istream&,Point&);
friend int operator==(const Point&,const Point&);
friend Point operator+(const Point&,const Point&);
friend Point operator&(Point&, Point&);
public:
double x,y,z;

Point(double a=0,double b=0,double c=0): x(a),y(b),z(c) {}
Point(const Point& p): x(p.x),y(p.y),z(p.z){}
Point& operator=(const Point&);
void negate(){x *= -1;y *= -1;z *= -1;}
double norm(){ return sqrt(x*x+y*y+z*z);}
operator Vector();//conversion operator
double & operator[](int);
};
std::ostream& operator<<(std::ostream & ost,const Point & r)
{
std::cout<<"(";
ost<<r.x<<","<<r.y<<","<<r.z;
std::cout<<")";
return ost;
}
std::istream& operator>>(std::istream & ist,Point & r)
{
std::cout<<"x:\n";
ist>>r.x;
std::cout<<"y:\n";
ist>>r.y;
std::cout<<"z:\n";
ist>>r.z;
return ist;
}
int operator==(const Point& p,const Point& q)
{
if(p.x != q.x && p.y != q.y && p.z!=q.z) return 0;
else
   return 1;
}
Point& Point::operator=(const Point& p)
{
x=p.x;
y=p.y;
z=p.z;
return *this;
}
Point operator+(const Point& v,const Point& w){
Point k;
k.x= v.x+w.x;
k.y=v.y+w.y;
k.z=v.z+w.z;
return k;
}
double & Point::operator[](int l)
{
if (l==1) return x;
if (l==2) return y;
if (l==3) return z;
std::cerr<<"Error: index out of range\n";
exit(0);
}
Point operator&(Point& v, Point & w)
{
Point z( v.y*w.z-v.z*w.y,v.z*w.x-v.x*w.z,v.x*w.y-w.x*v.y);
return z;
}
Point::operator Vector()
{
  Vector g(3);
g.a=x;
g.b=y;
g.b=z;
return g;
}
int main()
{
Point m,n,o,l;
std::cin>>m>>n;
std::cout<<"m: "<<m<<"\nn: "<<n;
l=n;
std::cout<<"\nl is assigned value of n.\nl: "<<l<<" \n";
std::cout<<"o=m+n\n";
std::cout<<"o: "<<o;
Point s;
s=m&n;
std::cout<<"\nCross product of m and n:\ns: "<<s;
std::cout<<"\ns.negate():\n";
s.negate();
std::cout<<s;
std::cout<<"\ns.norm():\n";
double b;
b=s.norm();
std::cout<<b;
Point k;
Vector t = Vector(k);
std::cout<<"\nPoint k: "<<k;
std::cout<<"\nVector t: "<<t;
return 0;
}

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Compilation time: 0.52 sec, absolute running time: 0.15 sec, cpu time: 0.01 sec, memory peak: 5 Mb, absolute service time: 0,83 sec