Well-known algorithmic competition hack to represent points in euclidean space as complex numbers to get the distance between them by subtracting the two complex numbers.

gistfile1.cpp

#include<complex>
#include<cmath>
#include<iostream>
using namespace std;

typedef complex<double> Point;

#define x imag()
#define y real()

int main()
{
  Point p1(5,5);
  Point p2(9,2);

  cout << abs(p1 - p2) << endl; // Eucledian distance between two points

  return 0;
}