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POI'm having trouble with operator overloading of the operator- function
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copied!<p>The compiler gives me an error when trying to subtract two Point3D objects. I get this error:</p> <pre><code>Invalid operands to binary expression ('Point3D' and 'Point3D') </code></pre> <p>This is what I have in my Vector3D.h:</p> <pre><code>#include "Point3D.h" using namespace std; class Vector3D { friend const Point3D operator+(const Point3D& a, const Vector3D& b); friend const Vector3D operator-(const Point3D& a, const Point3D& b); public: Vector3D() {} Vector3D(float x, float y, float z); Vector3D(Point3D const& originPoint, float theta, float distance); float getX() const {return x;} float getY() const {return y;} float getZ() const {return z;} static Vector3D minus(Point3D const& destination, Point3D const& origin); Vector3D operator-(Vector3D const& other) const; float dot(Vector3D const& other) const; static float angleBetweenTwoVectorsZeroToPi(Vector3D const& a, Vector3D const& b); static float angleBetweenTwoVectorsZeroToTwoPi(Vector3D const& a, Vector3D const& b); Vector3D normalize() const; float length() const; //const float * const getArray() const {return &x;} Vector3D multiply(float scalar) const; bool operator==(Vector3D const& v) const; float operator[] (int i) const; private: float x; float y; float z; }; </code></pre> <p>The Vector3D.cpp file which defines the binary operators:</p> <pre><code>#include "Vector3D.h" #include "Math3D.h" #include <math.h> #include "MathConstants.h" Vector3D::Vector3D(float x, float y, float z): x(x), y(y), z(z) {} Vector3D::Vector3D(Point3D const& originPoint, float theta, float distance) { Point3D endPoint = Math3D::calcaultePoint3D(originPoint, theta, distance); Vector3D result = minus(endPoint, originPoint); this->x = result.x; this->y = result.y; this->z = result.z; } Vector3D Vector3D::minus(Point3D const& destination, Point3D const& origin) { return Vector3D(destination.getX() - origin.getX(), destination.getY() - origin.getY(), destination.getZ() - origin.getZ()); } Vector3D Vector3D::operator-(Vector3D const& other) const { return Vector3D(x-other.x, y-other.y, z-other.z); } float Vector3D::dot(const Vector3D &other) const { return x * other.x + y * other.y + z * other.z; } float Vector3D::length() const { return sqrtf(dot(*this)); } Vector3D Vector3D::normalize() const { float len = length(); return Vector3D(getX()/len, getY()/len, getZ()/len); } Vector3D Vector3D::multiply(float scalar) const { return Vector3D(x * scalar, y * scalar, z * scalar); } float Vector3D::angleBetweenTwoVectorsZeroToPi(const Vector3D &a, const Vector3D &b) { /* * The result is between 0 and PI */ Vector3D unitA = a.normalize(); Vector3D unitB = b.normalize(); return acos(unitA.dot(unitB)); } bool Vector3D::operator==(const Vector3D &v) const { return (x == v.x) && (y == v.y) && (z == v.z); } float Vector3D::operator[](int i) const { return (&x)[i]; } float Vector3D::angleBetweenTwoVectorsZeroToTwoPi(const Vector3D &a, const Vector3D &b) { /* * The result is between 0 and 2PI * * "Assuming a = [x1,y1] and b = [x2,y2] are two vectors with their bases at the * origin, the non-negative angle between them measured counterclockwise * from a to b is given by * * angle = mod(atan2(x1*y2-x2*y1,x1*x2+y1*y2),2*pi); * * As you can see, this bears a close relationship to the three-dimensional * formula I wrote last July 10. The quantities, x1*y2-x2*y1 and x1*x2+y1*y2 * are, respectively, the sine and cosine of the counterclockwise angle from * vector a to vector b, multiplied by the product of their norms - that is, their * cross product and the dot product restricted to two dimensions. The 'atan2' * function then gives the angle between them ranging from -pi to +pi, and the * 'mod' operation changes this so as to range from 0 to 2*pi, as you requested." * * Roger Stafford * http://www.mathworks.com/matlabcentral/newsreader/view_thread/151925 */ float resultNegPiToPosPi = atan2f(a.x*b.y-b.x*a.y, a.x*b.x+a.y*b.y); if (resultNegPiToPosPi < 0.0f) { resultNegPiToPosPi = resultNegPiToPosPi + 2*MathConstants::PI; } return resultNegPiToPosPi; } const Point3D operator+(const Point3D& a, const Vector3D& b) {return Point3D(a.getX()+b.getX(), a.getY()+b.getY(), a.getZ()+b.getZ());} const Vector3D operator-(const Point3D& a, const Point3D& b) {return Vector3D(a.getX()-b.getX(), a.getY()-b.getY(), a.getZ()-b.getZ());} </code></pre> <p>This is where I try to subtract a Point3D from another:</p> <pre><code>void AnimationService::handlePlayerMovement(double lastTime, double currentTime, Vector3D vector) { Point3D a; Point3D b; Vector3D result = a - b; // this is the problem line } </code></pre> <p>The strange part is that the binary <code>operator+</code> does work, but for some reason <code>operator-</code> gives me the error. Can anyone tell me what I'm doing wrong?</p>

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