Erlang Programmingのchapter3のexciseを途中まで
本日のErlang Lite #2の予習なんだけど,もう眠くなったのであきらめる!!
なので中途半端に途中までw.
Ex.3-1
%% ex1.erl -module(ex1). -compile(export_all). sum(1) -> 1; sum(N) -> N + sum(N-1). sum(N, M) -> if N == M -> N; N < M -> M + sum(N, M-1) end.
Ex.3-2
%% ex2.erl -module(ex2). -compile(export_all). create(0) -> []; create(N) -> create(N-1) ++ [N]. reverse_create(0) -> []; reverse_create(N) -> [N|create(N-1)].
Ex.3-3
%% ex3.erl -module(ex3). -compile(export_all). printnum(0) -> ok; printnum(N) -> io:format("Number:~p~n",[N]), printnum(N-1). printevennum(0) -> ok; printevennum(N) when N rem 2 == 0 -> io:format("Number:~p~n",[N]), printevennum(N-1); printevennum(N) -> printevennum(N-1).
Ex.3-4
%% db.erl -module(db). -compile(export_all). new() -> []. %% reserved function destroy(Db) -> ok. write(Key, Element, Db) -> [{Key,Element}|Db]. delete(Key, Db) -> case Db of [] -> []; [H|T] -> case H of {Key, Element} -> delete(Key,T); _ -> [H|delete(Key,T)] end end. read(Key, Db) -> case Db of [] -> {error, instance}; [H|T] -> case H of {Key, Element} -> {ok, Element}; _ -> read(Key,T) end end. match(Element, Db) -> case Db of [] -> []; [H|T] -> case H of {Key, Element} -> [Key|match(Element,T)]; _ -> match(Element,T) end end.
Ex.3-5
%% ex5.erl -module(ex5). -compile(export_all). filter(List, Target) -> case List of [] -> []; [Target|_T] -> [Target]; [H|T] -> [H|filter(T,Target)] end. reverse(List) -> case List of [] -> []; [H|T] -> reverse(T) ++ [H] end. concatenate(Lists) -> case Lists of [] -> []; [H|T] -> H ++ concatenate(T) end. flatten(List) -> case List of [] -> []; [H|T] when is_list(H) -> concatenate([flatten(H)|[flatten(T)]]); [H|T] -> [H|flatten(T)] end.
Ex.3-6 (quick sort)
%% ex6.erl -module(ex6). -compile(export_all). %% WikipediaのErlangのページのコードが参考になる quicksort([]) -> []; quicksort(List) -> case List of [Pivot|Rest] -> quicksort([ X || X <- Rest, X < Pivot]) ++ [Pivot] ++ quicksort([ Z || Z <- Rest, Z >= Pivot]) end.
