#let rec print_arbre print_étiquette print_feuille arbre = 
 match arbre with
 | Vide -> ()
 | Feuille f -> print_feuille f
 | Noeud {Étiquette = e;Fils_gauche = fg;Fils_droit = fd} ->
     print_string "(";
     print_arbre print_étiquette print_feuille fg;
     print_étiquette e; 
     print_arbre print_étiquette print_feuille fd;
     print_string ")";;
print_arbre : ('a -> 'b) -> ('c -> unit) -> ('a, 'c) arbre 
-> unit = <fun>
#print_arbre print_int print_int mon_arbre;;
(((2)5(8))10(30(40)))- : unit = ()

#let print_op op = match op with
 | Addition -> print_string "+"
 | Soustraction -> print_string "-"
 | Multiplication -> print_string "*"
 | Division -> print_string "/";;
print_op : op -> unit = <fun>
#print_arbre print_op print_int mon_expr;;
((1*2)+(3-(4/5)))- : unit = ()