From: "sebastien FURIC" <sebastien.furic@tni-valiosys.com>
To: OCaml Mailing list <caml-list@inria.fr>
Subject: [Caml-list] Question
Date: Mon, 01 Dec 2003 16:41:02 +0100 [thread overview]
Message-ID: <3FCB610E.932B363B@tni.fr> (raw)
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.
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next reply other threads:[~2003-12-01 15:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-01 15:41 sebastien FURIC [this message]
2003-12-01 17:48 ` Remi Vanicat
2003-12-01 18:04 ` sebastien FURIC
2003-12-03 14:02 ` Damien Doligez
2003-12-10 10:27 ` Pierre Weis
2003-12-10 15:53 ` skaller
2003-12-11 9:52 ` Luc Maranget
2003-12-11 14:20 ` skaller
2003-12-11 16:56 ` Luc Maranget
2005-05-23 6:54 Question dsingh01
2005-05-23 7:40 ` [Caml-list] Question Remi Vanicat
2005-05-23 12:21 ` Jacques Carette
2005-06-08 10:06 question dsingh01
2005-06-08 15:13 ` [Caml-list] question Damien Bobillot
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