(*  Tail Recursion Experiment 

  While loops and for loops are available in F#.  However, with the
pattern-matching style of programming recursion is often the most natural
way to write a function.  Therefore it is crucial to distinguish between
tail and non-tail recursion.  This experiment will demonstrate that F#
will optimize tail recursion like Scheme and C.  Java/C# does not optimize
tail recursion (except for specialized compilers) because of dynamic 
dispatch: the version of the function called is not determined at compile 
time.  However, F#'s pattern matching mechanism replaces dynamic dispatch.
*)

open System;;

let rec f = function
  | n when n<2 -> n
  | n -> 1 + f(n-1);;

let rec g = function
  | n when n<2 -> printfn "done"
  | n -> if n%100=0 then printf "%d " n;
         g(n-1);;

// which one is tail-recursive?   g.

g(1000000);;  // runs without problems because of tail recursion optimization

let x = f(1000000);; // will crash with stack overflow exception