Implement operator== and operator< in Triangle

QTProject/triangle.cpp

@@ -50,6 +50,32 @@ Triangle &Triangle::operator=(const Triangle &other) {
     return *this;
 }
 
+bool Triangle::operator==(const Triangle &other) const {
+    return u_ == other.u_ && v_ == other.v_ && w_ == other.w_;
+}
+
+bool Triangle::operator<(const Triangle &other) const {
+    if (u_ < other.u_) {
+        return true;
+    } else if (u_ > other.u_) {
+        return false;
+    }
+
+    if (v_ < other.v_) {
+        return true;
+    } else if (v_ > other.v_) {
+        return false;
+    }
+
+    if (w_ < other.w_) {
+        return true;
+    } else if (w_ > other.w_) {
+        return false;
+    }
+
+    return false;
+}
+
 QDebug operator<<(QDebug d, const Triangle &triangle) {
     QDebugStateSaver saver(d);
     d.nospace() << "Triangle(" << triangle.u_idx() << ", " << triangle.v_idx() << ", " << triangle.w_idx() << "; " << triangle.u().pos << ", " << triangle.v().pos << ", " << triangle.w().pos << ")";

QTProject/triangle.h

@@ -22,6 +22,11 @@ class Triangle {
 
         Triangle &operator=(const Triangle &other);
 
+        // == and < both ignore the vertex buffer, they only compare indices.
+        // They are implemented so that Triangle can be used as the key of a QMap.
+        bool operator==(const Triangle &other) const;
+        bool operator<(const Triangle &other) const;
+
     private:
         QVector<Vertex> vertex_buffer_;
         int u_;