[403-add-stdist-warnings] added str fct to levelpair

src/lib2_mesh/mesh/Mesh.hpp

@@ -24,6 +24,13 @@ struct LevelPair {
   LevelPair CoarserInTime() const { return LevelPair{space, time - 1}; }
 
   LevelPair Next() const { return LevelPair{space + 1, time + 1}; }
+
+  std::string str() const {
+    std::stringstream ss;
+    ss << "[" << space << ", " << time << "]";
+    return ss.str();
+  }
+
 };
 
 inline bool operator==(const LevelPair &l1, const LevelPair &l2) {