(*
CSE 341, Autumn 2010
Code written in lecture #2 (Fri 2010/10/01)
*)

(* Converts a single name from (last, first) to "first, last" format. *)
fun singleName(first, last) = last ^ ", " ^ first;

(* crappy version of singleName that treats the parameters as a tuple. *)
fun singleName2(t : string * string) =
	#2(t) ^ ", " ^ #1(t);

(* Converts a list of names from (last, first) format to a list of names
   in "first, last" format. *)
fun convertNames(names) =
	if names = [] then []
	else singleName(hd(names)) :: convertNames(tl(names));

(* test data for convertNames *)
val test1 = [("Hillary", "Clinton"), ("Barack", "Obama"), ("Joe", "Biden"),
             ("John", "McCain"), ("Ron", "Paul")];


(* Produces the larger of the two values passed. *)
fun max(a, b) = if a > b then a else b;

(* alternative version of max that treats its parameters as a tuple.
   not recommended style; merely used to illustrate that all functions so far
   really take just a single parameter: a tuple. *)
fun max2(twoInts : int * int) =
	if #1(twoInts) > #2(twoInts) then #1(twoInts)
	else #2(twoInts);


(* Functions that simply return their parameters.
   These are used to illustrate the idea of parametric polymorphism. *)
fun identity(x) = x;
fun identity2(x, y) = (x, y);
fun identity3(x, y) = [x, y];


(* Produces the last value from the given list.
   Precondition: List is non-empty. *)
fun last(lst) =
	if length(lst) = 1 then hd(lst)
	else last(tl(lst));

(* Computes n!, or 1 * 2 * 3 * ... * n-1 * n.
   Precondition: n >= 0. *)
fun factorial(n) =
	if n = 0 then 1
	else n * factorial(n - 1);