C-Code

#include <iostream>
#include <cmath>
#include <iterator>

template<typename T>
T square(T a) { return a*a; }

template<typename T>
struct Point
{
    T x, y;

    static Point from_command_line()
    {
        #define do_for(what) (std::cout << #what ": ", *std::istream_iterator<T>(std::cin))
        return { do_for(x), do_for(y) };
    }

    double distance_to(Point const& p)
    {
        return ::sqrt( square( ::abs(p.y - y) ) + square( ::abs(p.x - x) ) );
    }
};

#include <iomanip>
#include <limits>

int main()
{
    auto p1 = Point<int>::from_command_line(),
         p2 = Point<int>::from_command_line();

    std::cout << "distance: " << std::setprecision( std::numeric_limits<double>::digits10 ) << std::fixed << p1.distance_to(p2);
}