]> Hi, What do you think of the following code? # type toto = Toto of int | Titi of string;; type toto = Toto of int | Titi of string # let test t t' = match t, t' with | ((Toto _ | Titi _), Toto x | Toto x, (Toto _ | Titi _)) when x = 0 -> "OK" | _ -> "KO";; Characters 73-79: Warning: this pattern is unused. | ((Toto _ | Titi _), Toto x | Toto x, (Toto _ | Titi _)) when x = 0 -> "OK" ^^^^^^ val test : toto -> toto -> string = <fun> # test (Toto 0) (Toto 1);; - : string = "KO" I was expecting "when" to be right distributive over "|". I find OCaml's behaviour not very intuitive in such a situation. The correct code is: # let test t t' = match t, t' with | (Toto _ | Titi _), Toto x when x = 0 -> "OK" | Toto x, (Toto _ | Titi _) when x = 0 -> "OK" | _ -> "KO";; val test : toto -> toto -> string = <fun> # test (Toto 0) (Toto 1);; - : string = "OK" Is there a good reason for this? Cheers, Sébastien. ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners