Lesson21

#include <cmath>
#include <iomanip>
#include <iostream>
using namespace std;
struct Point {
  double x;
  double y;
};
struct Vector {
  double x;
  double y;
};
Vector operator-(const Point& p1, const Point& p2) {return {p1.x - p2.x, p1.y - p2.y};}
Vector operator+(const Vector& v1, const Vector& v2) {return {v1.x + v2.x, v1.y + v2.y};}
Vector operator-(const Vector& v1, const Vector& v2) {return {v1.x - v2.x, v1.y - v2.y};}
Point operator+(const Point& p, const Vector& v) {return {p.x + v.x, p.y + v.y};}
double DotProduct(const Vector& v1, const Vector& v2) {return v1.x * v2.x + v1.y * v2.y;}
double CrossProduct(const Vector& v1, const Vector& v2) {return v1.x * v2.y - v1.y * v2.x;}

int main() {
  Vector v1 = {3, 4}, v2 = {0, 5};
  cout << DotProduct(v1, v2) << endl;
  cout << CrossProduct(v2, v1) << endl;
  Point p1{2, 2}, p2{6, 5};
  Vector v3 = p2 - p1;
  cout << v3.x << " " << v3.y << endl;
  return 0;
}

int main1() {
  int n = 0;
  Point p;
  p.x = 5.0;
  p.y = acos(-1);
  cout << fixed << p.x << " " << setprecision(10) << p.y << endl;
  cout << p.x << " " << p.y << endl;
  return 0;
}