Ackermann in F#

Ackermann is a recursive function with a tendency to generate large numbers like there's no tomorrow. I've decided to implement it on F# as a part of my learning process.

Here is my first attempt:

let rec ackermann m n =
if m = 0 then
  n + 1
else
  if n = 0 then
      ackermann (m - 1) 1
  else
      ackermann (m - 1) (ackermann m (n - 1))

Ok, not as impressive as those great samples I've been browsing on the net, but still a challenge to write for an old curly brackets developer. Here's what I found hard:

• tabs not allowed;
  
• initially no brackets or BEGIN/END to create blocks (#light pragma) was a problem; surprising as it may seem, this was easily absorved - now I just love it (probably because I didn't have to code a syntactic analyser for F#);
• parameters are still hard to code; not just to define, but also to push; no comma here - except for non F# CLR methods...
  
• the error messages are not yet natural to me; ex: "found int -> int when expecting int * int"
  

I confess it took me a some try and error until I got it right - it kind of remember when I learned C back in 1988: try structure.member; doesn't compile? try structure->member; Thank god for the great IDE.

Then I've tried the pattern matching way of live.

let rec ackermann m n =
match m, n with
   0, n -> n + 1
 | m, 0 -> ackermann (m - 1) 1
 | m, n -> ackermann (m - 1) (ackermann m (n - 1))

It seems more FSharpish, right? My next step could very well be a memoization approach, who knows. One thing's for sure: learning a new language is a lesson on humbleness - I feel like a total ignorant! :)

[update]

Here are my results (ok, the table comes from wikipedia):

m\n	0	1	2	3	4
0	1	2	3	4	5
1	2	3	4	5	6
2	3	5	7	9	11
3	5	13	29	61	125
4	13	Stack Fault	Stack Fault	Stack Fault	Stack Fault
5	Stack Fault	Stack Fault	Stack Fault	Stack Fault	Stack Fault

The results are not a complete surprise. What comes as a surprise to me is that both my cores were in use during the test. Is it possible?