Math Vector Template

Haven't yet tested well, might have some bugs.

#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-10;
const double PI = acos( -1.0 );

int dcmp(double x){
    if( fabs( x ) < EPS ) return 0;
    return x < 0 ? -1 : 1;
}
struct Vector{
    double x, y;
    Vector(double _x = 0, double _y = 0):x(_x),y(_y){}
    friend Vector operator + (Vector A, Vector B){ return Vector( A.x + B.x, A.y + B.y ); }
    friend Vector operator - (Vector A, Vector B){ return Vector( A.x - B.x, A.y - B.y ); }
    friend Vector operator * (Vector A, double p){ return Vector( A.x * p, A.y * p ); }
    friend Vector operator / (Vector A, double p){ return Vector( A.x / p, A.y / p ); }
    friend bool operator < (const Vector &A, const Vector &B){ return A.x < B.x || ( A.x == B.x && A.y < B.y ); }
    friend bool operator == (const Vector &A, const Vector &B){ return A.x == B.x && A.y == B.y; }
    friend bool operator <= (const Vector &A, const Vector &B){ return A < B || A == B; }
    friend bool operator > (const Vector &A, const Vector &B){ return !( A <= B ); }
    friend bool operator >= (const Vector &A, const Vector &B){ return !( A < B ); }
    friend double Dot(Vector A, Vector B){ return A.x * B.x + A.y * B.y; }
    friend double Length(Vector A){ return sqrt( Dot( A, A ) ); }
    friend double Angle(Vector A, Vector B){ return acos( Dot( A, B ) / Length( A ) / Length( B ) ); }
    friend double Cross(Vector A, Vector B){ return A.x * B.y - A.y * B.x; }
    friend double Area2(Vector A, Vector B, Vector C){ return Cross( B - A, C - A ); }
    friend Vector Rotate(Vector A, double rad){
        return Vector( A.x * cos(rad) - A.y * sin(rad), A.x * sin(rad) + A.y * cos(rad) );
    }
    friend Vector Normal(Vector A){
        double L = Length( A );
        return Vector( -A.y / L, A.x / L );
    }
    friend Vector GetLineIntersection(Vector P, Vector v, Vector Q, Vector w){
        Vector u = P - Q; // P + tv, Q + tw, intersection, make sure there is one before calling!
        double t = Cross( w, u ) / Cross( v, w ); // make sure Cross( v, w ) != 0, -> not parallel
        return P + v * t;
    }
    friend double DistanceToLine(Vector P, Vector A, Vector B){
        Vector v1 = B - A, v2 = P - A; // returns distance perpendicular to line AB
        return fabs( Cross( v1, v2 ) ) / Length( v1 );
    }
    friend double DistanceToSegment(Vector P, Vector A, Vector B){ // returns distance from p to segment AB
        if( A == B ) return Length( P - A );
        Vector v1 = B - A, v2 = P - A, v3 = P - B;
        if( dcmp( Dot( v1, v2 ) ) < 0 ) return Length( v2 );
        else if( dcmp( Dot( v1, v3 ) > 0 ) ) return Length( v3 );
        return fabs( Cross( v1, v2 ) ) / Length( v1 );
    }
    friend Vector GetLineProjection(Vector P, Vector A, Vector B){
        Vector v = B - A;
        return A + v * ( Dot( v, P - A ) / Dot( v, v ) );
    }
    friend bool SegmentProperIntersection(Vector a1, Vector a2, Vector b1, Vector b2){
        double c1 = Cross( a2 - a1, b1 - a1 ), c2 = Cross( a2 - a1, b2 - a1 ),
               c3 = Cross( b2 - b1, a1 - b1 ), c4 = Cross( b2 - b1, a2 - b1 );
        return dcmp( c1 ) * dcmp( c2 ) < 0 && dcmp( c3 ) * dcmp( c4 ) < 0;
    }
    friend double PolygonArea(vector<Vector> p){
        double area = 0;
        int n = p.size();
        for(int i = 1; i < n - 1; ++i)
            area += Cross( p[i] - p[0], p[i + 1] - p[0] );
        return area / 2; // might be - signed, haven't tried yet
    }
    friend bool isPointOnSegment(Vector p, Vector a1, Vector a2){
        return dcmp( Cross( a1 - p, a2 - p ) == 0 && dcmp( Dot( a1 - p, a2 - p ) ) < 0 );
    }
    friend int isPointInPolygon(Vector p, vector<Vector> poly){
        int wn = 0;
        int n = poly.size();
        for(int i = 0; i < n; ++i){
            if( isPointOnSegment( p, poly[i], poly[(i + 1) % n] ) ) return -1; // on border
            int k = dcmp( Cross( poly[(i + 1) % n] - poly[i], p - poly[i] ) );
            int d1 = dcmp( poly[i].y - p.y );
            int d2 = dcmp( poly[(i + 1) % n].y - p.y );
            if( k > 0 && d1 <= 0 && d2 > 0 ) ++wn;
            if( k < 0 && d2 <= 0 && d1 > 0 ) --wn;
        }
        if( wn != 0 ) return 1;
        return 0;
    }
    friend vector<Vector> ConvexHull(vector<Vector> p){
        sort( p.begin(), p.end() );
        p.erase( unique( p.begin(), p.end() ), p.end() );
        int m = 0;
        int n = p.size();
        vector<Vector> ch( n + 1 );
        for(int i = 0; i < n; ++i){
            while( m > 1 && Cross( ch[m - 1] - ch[m - 2], p[i] - ch[m - 2] ) <= 0 ) --m;
            ch[ m++ ] = p[i];
        }
        int k = m;
        for(int i = n - 2; i >= 0; --i){
            while( m > k && Cross( ch[m - 1] - ch[m - 2], p[i] - ch[m - 2] ) <= 0 ) --m;
            ch[ m++ ] = p[i];
        }
        if( n > 1 ) --m;
        ch.resize( m );
        return ch;
    }
};


int main(){
        

    return 0;
}