pass as reference

ml.cpp

@@ -1768,7 +1768,7 @@ void load_std_lib(MlEnvironment &env) {
 }
 
 // Does this environment, or its parent environment, have a variable?
-bool MlEnvironment::has(std::string name) const {
+bool MlEnvironment::has(const std::string &name) const {
 	// Find the value in the map
 	std::map<std::string, MlValue>::const_iterator itr = defs.find(name);
 	if (itr != defs.end())