Sunny's Tech Blog

ML Nested Pattern ⇒ C++ third party Mach7

c++은 nested pattern을 지원함 in third party(standard 아님)

ML Exception ⇒ C++ Exception

✅ excpetion을 사용하려면 #include 을 추가해야함 </aside> **defining new exception** - exception을 상속받아서 structure을 만들면 됨 ```jsx #include struct MyException: public std::excpetion { // std::exception에 있는 virtual 함수임!,throw하지 않는다는 의미임 const char* what() const throw() {return "excpetion";} }; ``` **raise exceptions and handling them** - 동일하게 top to bottom으로 catch됨 ```jsx try { std::cout <<"던진다"<<std::endl; throw MyException(); } catch(MyException& e) { std::cout <<"받는다"<<std::endl; std::cout << e.what()<<std::endl; //exception, 해당 what을 재정의하지 않으면 std::exception이 출력됨 } catch(std::exception& e) { ... } ``` ![스크린샷 2023-04-15 오후 1.00.11.png](lec04%20cpp-fp%206e19f108c5d347ef96d56c75e90e0aa5/%25E1%2584%2589%25E1%2585%25B3%25E1%2584%258F%25E1%2585%25B3%25E1%2584%2585%25E1%2585%25B5%25E1%2586%25AB%25E1%2584%2589%25E1%2585%25A3%25E1%2586%25BA_2023-04-15_%25E1%2584%258B%25E1%2585%25A9%25E1%2584%2592%25E1%2585%25AE_1.00.11.png) ### Tail Recusion - C++ 컴파일러는 tail recursion optimization을 지원함 - calling/retruning form function하지 않고 tail call은 loop로 바뀜 ![스크린샷 2023-04-15 오후 1.01.24.png](lec04%20cpp-fp%206e19f108c5d347ef96d56c75e90e0aa5/%25E1%2584%2589%25E1%2585%25B3%25E1%2584%258F%25E1%2585%25B3%25E1%2584%2585%25E1%2585%25B5%25E1%2586%25AB%25E1%2584%2589%25E1%2585%25A3%25E1%2586%25BA_2023-04-15_%25E1%2584%258B%25E1%2585%25A9%25E1%2584%2592%25E1%2585%25AE_1.01.24.png) ![스크린샷 2023-04-15 오후 1.01.43.png](lec04%20cpp-fp%206e19f108c5d347ef96d56c75e90e0aa5/%25E1%2584%2589%25E1%2585%25B3%25E1%2584%258F%25E1%2585%25B3%25E1%2584%2585%25E1%2585%25B5%25E1%2586%25AB%25E1%2584%2589%25E1%2585%25A3%25E1%2586%25BA_2023-04-15_%25E1%2584%258B%25E1%2585%25A9%25E1%2584%2592%25E1%2585%25AE_1.01.43.png) nontail → tail로 바꿀 때 acc를 추가로 받는 helper function을 만들어서 해결 - 예시에서는 helper function을 밖에 둠 - 안에 둘려면 람다함수여야하는데 람다함수는 structure of instance를 만든 후 recursive manner를 하기때문에 overhead가 있기 때문에 빠르게 되지 않아서 helper function을 밖에 둔 것! 애초부터 빠르게 하려고 하는데 람다함수떄문에 느리게 되니까~ reverse를 nontail → tail로 바꿔라고 저번에 했었음 ![스크린샷 2023-04-15 오후 1.03.45.png](lec04%20cpp-fp%206e19f108c5d347ef96d56c75e90e0aa5/%25E1%2584%2589%25E1%2585%25B3%25E1%2584%258F%25E1%2585%25B3%25E1%2584%2585%25E1%2585%25B5%25E1%2586%25AB%25E1%2584%2589%25E1%2585%25A3%25E1%2586%25BA_2023-04-15_%25E1%2584%258B%25E1%2585%25A9%25E1%2584%2592%25E1%2585%25AE_1.03.45.png) ```jsx #include #include "List.h" List rev_aux (List xs,List acc) { if (xs.isEmpty()) { return acc; } else { return rev_aux(xs.tail(), cons(xs.head(), acc)); } } List rev (List xs) { // if (xs.isEmpty()) { // return List(); // } else { // cons(rev(xs.tail()) ,xs.head()); // } return rev_aux(xs,List{}); } int main(void) { List a = makeList(1,2,3); print(a); print(rev(a)); } ```