-void instr_new_variable_type(std::string new_typename, std::string color);
-void instr_new_user_variable_type(std::string father_type, std::string new_typename, std::string color);
-void instr_new_user_state_type(std::string father_type, std::string new_typename);
-void instr_new_value_for_user_state_type(std::string new_typename, const char* value, std::string color);
+void instr_new_variable_type(const std::string& new_typename, const std::string& color);
+void instr_new_user_variable_type(const std::string& father_type, const std::string& new_typename,
+ const std::string& color);
+void instr_new_user_state_type(const std::string& father_type, const std::string& new_typename);
+void instr_new_value_for_user_state_type(const std::string& new_typename, const char* value, const std::string& color);