Implement != for Triangle

QTProject/triangle.cpp

@@ -139,6 +139,10 @@ bool Triangle::operator==(const Triangle &other) const {
     return u_ == other.u_ && v_ == other.v_ && w_ == other.w_;
 }
 
+bool Triangle::operator!=(const Triangle &other) const {
+    return !(*this == other);
+}
+
 bool Triangle::operator<(const Triangle &other) const {
     if (u_ < other.u_) {
         return true;

QTProject/triangle.h

@@ -55,6 +55,7 @@ class Triangle {
         // == 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;
         bool operator<(const Triangle &other) const;
 
         bool next_ctrclockwise(Edge first, Edge next) const;