refactorings

main.cpp

@@ -117,7 +117,7 @@ void repl() {
 				result->print();
 
 				code += input + "\n";
-			} catch (std::exception &e) {
+			} catch (const std::exception &e) {
 				std::cerr << e.what() << std::endl;
 			}
 		}