Linked List OCaml

How would I create a linked list to hold my data in OCaml? I'm trying to make a singly linked list, however I'm having trouble with the syntax. I just want to make a module to simply get the 'a from the linked list, insert 开发者_如何学编程'a or delete 'a.

Anyone have any idea?

As aneccodeal told, ocaml already has lists.

However, for your interest, this is how you could build your own list. Obviously, you would never use it on a real application :) If you want to have some trees, the data structure would be very similar.

exception Empty_list

type 'a my_list = Nil | List of 'a * 'a my_list

let head = function 
     Nil -> raise Empty_list
   | List(e,_) -> e;;

let tail = function
    Nil -> Nil
   | List(_,t) -> t

let l = List(1, List(4, List(8, Nil)));;

print_endline (string_of_int(head l));;

print_endline (string_of_int (head(tail l)));;

OCaml has lists built in:

List of integers: [1;2;3;4;5] ;; returns: int list = [1; 2; 3; 4]

List of Strings: ["this";"that";"other"];; returns: string list = ["this"; "that"; "other"]

Or you can use the cons operator :: to build lists:

1::2::3::[];; returns: int list = [1; 2; 3]

To get the head (first item) of a list:

List.hd [1;2;3]
returns 1

To get the tail of a list (all items after the first item)

List.tl [1;2;3] returns: int list = [2; 3]

Also, you can have a look at how lists are implemented in the OCaml standard library by looking at:

[installation location for OCaml]/lib/ocaml/std-lib/list.ml

Doesn't OCaml already have lists as a primitive? I haven't done SML since college, but I seem to recall head and tail primitives. I see that other people have implemented a true linked list data structure out there though... check out Dustin's OCaml Linkedlist for example.