From: Pierre Weis <pierre.weis@inria.fr>
To: sebastien.furic@tni-valiosys.com (sebastien FURIC)
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Question
Date: Wed, 10 Dec 2003 11:27:59 +0100 (MET) [thread overview]
Message-ID: <200312101027.LAA20728@pauillac.inria.fr> (raw)
In-Reply-To: <3FCB610E.932B363B@tni.fr> from sebastien FURIC at "Dec 1, 103 04:41:02 pm"
[...]
> I was expecting "when" to be right distributive over "|". I find
> OCaml's behaviour not very intuitive in such a situation.
[...]
The when construct introduces a guard to a pattern matching
clause. This means that a when construct is global to the entire
pattern of the clause it appears in; it means in particular that no
when construct can be nested into a pattern and the question of its
distributivity wrt any other construct is pointless.
> Is there a good reason for this?
Yes: simplicity, complexity invariants preservation for runtime
pattern analysis decisions even in the presence of when clauses,
easier understanding of the compiler warnings, simplicity and
well-definedness semantics (in particular the desired invariance wrt
the order of evaluation).
> Cheers,
>
> Sébastien.
Best regards,
Pierre Weis
INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/
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next prev parent reply other threads:[~2003-12-10 10:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-01 15:41 sebastien FURIC
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 [this message]
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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