I don't understand the behavior of the following program (ocaml 3.01)

type couple = {p1 :int ;p2:int};;
let c1 = {p1=0;p2=10};;
let c2 = {p1=0;p2 = 20};;

let n = ref 0;;
let rec numero l =
  match l with
    | [] -> []
    | t::f ->n:=!n+1; {t with p1= !n }::numero f;;

(* 
# numero [c1;c2];;
- : couple list = [{p1=2; p2=10}; {p1=2; p2=20}]
*)

Why the fied p1 has the value 2 ?
Why it's different with the fonction numero'

let n' = ref 0;;
let rec numero' l =
  match l with
    | [] -> []
    | t::f -> n':=!n'+1; 
	let a = !n' in {t with p1= a }::numero' f;;
(* 
# numero' [c1;c2];;
- : couple list = [{p1=1; p2=10}; {p1=2; p2=20}]
*)

Thank you really much for any explanation.

-- 
Michel Levy
36 rue George Sand 38400 Saint Martin d'Hères
email : Michel.Levy@imag.fr
http://www-lsr.imag.fr/users/Michel.Levy/
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