Vector.h

#ifndef VECTOR_H_INCLUDED
#define VECTOR_H_INCLUDED
#define Point Vector

const double EPS = 1e-10;

struct Vector {
    double x, y;

    Vector(double x = 0, double y = 0) : x(x), y(y) {}

    Vector operator +(Vector B) {
        return Vector(x + B.x, y + B.y);
    }

    Vector operator -(Vector B) {
        return Vector(x - B.x, y - B.y);
    }

    Vector operator *(double k) {
        return Vector(k * x, k * y);
    }

    Vector operator /(double k) {
        return Vector(x / k, y / k);
    }

    bool operator ==(Vector B) {
        if(fabs(x - B.x) < EPS && fabs(y - B.y) < EPS) return true;
        else return false;
    }

    double dot(Vector B) {
        return x * B.x + y * B.y; //两向量的点积
    }

    double length() {
        return sqrt(x * x + y * y);
    }

    double cosAngleOfTwoVectors(Vector B) {
        return dot(B) / length() / B.length(); //两向量夹角的余弦值
    }

    double valueOfDet(Vector B) {
        return x * B.y - y * B.x; //两向量叉积的大小
    }

    Vector rotate(double rad) { //逆时针旋转rad弧度
        double s = sin(rad), c = cos(rad);
        return Vector(x * c - y * s, x * s + y * c);
    }

    Vector unitNormalVector() {
        double L = length(); //要保证A不是零向量
        return Vector(-y / L, x / L); //求单位法向量
    }
};

//typedef Vector Point;

#endif // VECTOR_H_INCLUDED