ocaml p6

p67.ml

(* Write a function val zip : 'a list * 'b list -> 'a * 'b list which accepts a 
* pair of lists of the same length and returns a list of pairs. For example,
* zip([1; 2; 3], ['A'; 'B'; 'C']) should return the list of pairs [(1, 'A'); (2,
* 'B'); (3, 'C')]. You may assume that the 2 input lists are of the same length.
* (2 Points)*)

let rec zip (a,b) =
  match (a,b) with
    ([],[]) -> []
    | ([],n::ns)-> []
    | (n::ns,[]) -> []
    | (k::ks, h::hs) -> (k,h)::zip(ks,hs);;

(* Write a function val unZip : 'a * 'b list -> 'a list * 'b list
* which accepts a list of pairs and returns a pair of lists. For example, unZip
* [(1, 'A'); (2, 'B'), (3, 'C')] should return the pair of lists ([1; 2; 3],
* ['A'; 'B'; 'C'])*)

let ua a = match a with (a,b)->a;;
let ub a = match a with (a,b)->b;;
let rec unzip list =
  match list with
    [] -> ([],[])
    | (a,b)::ns -> (a::ua(unzip(ns)),b::ub(unzip(ns)));;