generate all sublists of a list

sublists.ml

(*let A = [1;2;3]
 * genSublists A will yield
 * [[1]; [1; 2]; [1; 3]; [1; 2; 3];[2]; [2; 3]; [3]; []] *)

let rec gen list head =
    match list with
    [] -> []
    | first::rest -> let start = (head @ [first]) in
        let rec append list =
            match list with
            [] -> []
            | first'::rest' -> [start@[first']] @ append rest' in
            append rest @ (gen rest start);;

let rec genSublists list =
    match list with
    [] -> [[]]
    | first::rest as a -> [[first]] @ (gen a []) @ (genSublists rest);;