#include <iostream>
#include <cmath>
using namespace std;
struct Point {
double x;
double y;
};
struct Vector {
Point start;
Point end;
};
// pass by const reference; the function doesn't modify p1 or p2
Point subtract_points(const Point &p1, const Point &p2) {
Point delta;
delta.x = p1.x - p2.x;
delta.y = p1.y - p2.y;
return delta;
}
double length(const Vector &v) {
Point diff = subtract_points(v.start, v.end);
return sqrt(diff.x * diff.x + diff.y * diff.y);
}
int main() {
Vector v;
v.start.x = 1;
v.start.y = 0;
v.end.x = 2;
v.end.y = 1;
cout << "length of the vector is: " << length(v) << endl;
}
