#include <iostream>
#include <iomanip>
#include <utility>  // I want pair, which is in this.
#include <string>
#include <cmath>

using namespace std;

using point =  pair<double, double>;

namespace Euclid  {

    const string D_NAME = "Euclidian";
    int avar = 10;

    double Distance(point a, point b) {
         double dx, dy;
 
         dx = a.first- b.first;
         dy = a.second - b.second;

         return sqrt(dx*dx + dy*dy);
     }
}

namespace Manhattan {
    const string D_NAME = "MANHATTAN";
    int avar = 20;
    double Distance(point a, point b);
}

namespace Hausdorf {
    double Distance(point a, point b);
}

namespace Hausdorf {
     string D_NAME="Hausdorf";
     int avar = 30;
}

double Distance(point, point);

const string D_NAME= "Global";
int avar = 0;

using namespace Euclid;

namespace HD=Hausdorf;

ostream & operator << (ostream & s, const point &  p) {
    s << "(" << p.first <<", " << p.second << ")";
    return s;
}

int main() {

    point x1{0,0}, x2{10,5};

    cout << "Computing the distance from " << x1 << " to " << x2 << endl;

/*
    cout << "\t" << setw(10) << "Default"  
         << setw(10)  << Distance(x1, x2) << endl; 
*/
    cout << "\t" << setw(10) << ::D_NAME          
         << setw(10)  << ::Distance(x1, x2) << endl;
    cout << "\t" << setw(10) << Euclid::D_NAME  
         << setw(10)  << Euclid::Distance(x1, x2) << endl;
    cout << "\t" << setw(10) << Manhattan::D_NAME
         << setw(10)  << Manhattan::Distance(x1, x2) << endl;
    cout << "\t" << setw(10) << HD::D_NAME 
         << setw(10)  << HD::Distance(x1, x2) << endl;

    cout << endl;

    Euclid::avar = 10'000;

    cout << "The values of avar " << endl; 
    cout << ::D_NAME << " " << ::avar << endl;
    cout << Euclid::D_NAME << " " <<  Euclid::avar << endl;
    cout << Manhattan::D_NAME << " " << Manhattan::avar << endl;
    cout << Hausdorf::D_NAME << " " << Hausdorf::avar << endl;

    return 0;
}

double Distance(point, point){
    return 1;
}

double Manhattan::Distance(point a, point b) {
    double dx, dy;

    dx = abs(a.first- b.first);
    dy = abs(a.second - b.second);

    return (dx + dy);
}

namespace Hausdorf{
    double Distance(point a, point b) {
        double dx, dy;

        dx = abs(a.first- b.first);
        dy = abs(a.second - b.second);

        return max(dx, dy);
    }
}