基础计算几何

这两天准备学一点计算几何，先来一发基础的计算几何板子

#include <bits/stdc++.h>
using namespace std;
#define EPS (1e-8)

bool equals(double x, double y){
    return fabs(x-y) < EPS;
}

bool greater_than(double x, double y){
    return x - y > EPS;
}

struct Vec{
    double x, y;
    Vec(){};
    Vec(double _x, double _y): x(_x), y(_y){};
    
    Vec operator+(const Vec& v) const{
        return Vec(x+v.x, y+v.y);
    }
    Vec operator-(const Vec& v) const{
        return Vec(x-v.x, y-v.y);
    }
    Vec operator*(double d) const{
        return Vec(d*x, d*y);
    }
    Vec operator/(double d) const{
        return Vec(x/d, y/d);
    }
    double norm2()const{
        return x*x + y*y;
    }
};

double dot(const Vec& a, const Vec& b){
    return a.x * b.x + a.y * b.y;
}

double cross(const Vec& a, const Vec& b){
    return a.x * b.y - a.y * b.x;
}

typedef Vec Pt;