(*
 * This is an implementation of product in F#.
 * It's kind of ugly, though.  Compare with the
 * pattern-matching version in product2.fs
 *
 * @param nums A list of numbers.
 * @returns The result of multiplying all numbers in nums.
 *)
let rec product nums =
  // base case
  if nums = [] then
    1
  // recursive case: multiply the head element with
  //                 the rest of the list
  else
    (List.head nums) * product (List.tail nums)

// call product like this
product [1; 2; 3]