val i = ref 0;
while !i < 10 do
    (print(Int.toString(!i) ^ "\n");
     i := !i + 1);


fun multiply(x, 0) = 0
  | multiply(x, y) = x + multiply(x, y-1);

fun multiply(x, y) = 
    let
        val prod = ref 0
        val i = ref 0
    in
        (while  !i < y  do
             (prod := !prod + x;
              i :=  !i + 1);
         !prod)
    end;


fun exp(x, 0) = 1
  | exp(x, y) = x * exp(x, y-1);

fun exp(x, y) =
    let
        val expon = ref 1;
      val i = ref 0;
    in
        (while !i < y  do
            (expon := !expon * x;
              i := !i + 1);
         !expon)
    end;


fun gcd(a, 0) = a
  | gcd(a, b) = gcd(b, a mod b);

fun gcd(a0, b0)  =
    let
        val a = ref a0;
        val b = ref b0;
    in
        (while !b > 0 do
             let val r = !a mod !b
             in
                 (a := !b;
                  b := r)
             end;
         !a)
    end;

fun count([]) = 0
  | count(a::rest) = 1 + count(rest);

fun count(LL) =
    let
        val restLL = ref LL;
        val num = ref 0;
    in
        (while !restLL <> [] do
             (num := !num + 1;
              restLL := tl(!restLL));
         !num)
    end;



fun arithSum(1) = 1
  | arithSum(N) = N + arithSum(N-1);

fun arithSum(N) =
    let 
        val s = ref 0;
        val i = ref 1;  
    in
        (while !i <= N  do
             (s := !s + !i ;
              i := !i + 1);
         !s)
    end;


fun remainder(a, b) =
    let
        val q = a div b;
        val p = q * b;
        val r = a - p;
    in
        r
    end;

(* From Ex 6.10.1 *)

fun aaa(m) =
  let
    val x = ref 0;
    val i = ref 0;
  in
    (while !i < m do
      (x := !x + 2 * !i;
       i := !i + 1);
     !x)
  end;



fun exp(x, y) =
  let fun helper(a, 0) = a
        | helper(a, i) = helper(a * x, i-1);
  in
   helper(1, y)
  end; 

fun exp(x, y) =
    let 
        val a = ref 1;
        val i = ref y;
    in
       (while  !i > 0 do
            (i := !i - 1;
             a := !a * x);
        !a)
end;