OCaml 함수 예제

알아야 하는 것

for문

함수 구조

타입

리스트 인덱싱

match with

 

OCaml version 4.08.1

# let rec last = function
        | [] -> None
        | [x] -> Some x
        | _::t -> last t;;
val last : 'a list -> 'a option = <fun>
# last ["a";"b";"c";"d"];;
- : string option = Some "d"
# last [];;
- : 'a option = None
#

# let rec last_two = function
        | [] | [_] -> None
        | [x;y] -> Some (x,y)
        | _::t -> last_two t;;
val last_two : 'a list -> ('a * 'a) option = <fun>
# last_two ["a";"b";"c";"d"];;
- : (string * string) option = Some ("c", "d")
# last_two ["a"];;
- : (string * string) option = None

# let rec at k = function
        | [] -> None
        | h::t -> if k = 1 then Some h else at (k-1)  t;;
val at : int -> 'a list -> 'a option = <fun>
# at 3 ["a";"b";"c";"d";"e"];;
- : string option = Some "c"
# at 3 ["a"];;
- : string option = None

# let length list =
        let rec aux n = function
                | []->n
                | _::t -> aux (n+1) t
        in aux 0 list;;
val length : 'a list -> int = <fun>
# length ["a";"b";"c"];;
- : int = 3
# length [];;
- : int = 0

# let rev list =
        let rec aux acc = function
                | [] -> acc
                | h::t -> aux (h::acc) t in
        aux [] list;;
val rev : 'a list -> 'a list = <fun>
# rev ["a";"b";"c"];;
- : string list = ["c"; "b"; "a"]