From: Pierre Weis <weis@pauillac.inria.fr>
To: garrigue@kurims.kyoto-u.ac.jp (Jacques Garrigue)
Cc: caml-list@pauillac.inria.fr
Subject: Re: Ref syntax
Date: Fri, 22 Dec 2000 15:22:50 +0100 (MET) [thread overview]
Message-ID: <200012221422.PAA27513@pauillac.inria.fr> (raw)
In-Reply-To: <20001222183020R.garrigue@kurims.kyoto-u.ac.jp> from Jacques Garrigue at "Dec 22, 100 06:30:20 pm"
> Really, I don't think it would be useful at toplevel.
> I view let mutable .. in as a way to provide some state, but
> immediately cleanly wrapped, either by only being used locally, or
> in exported functions.
> This is completely similar to mutable object fields; both the goal and
> the method.
I hope this is effectively simple to type check, and ensure correct.
> > For instance, what do we
> > do if such a letref variable is assigned to, from within the body of a
> > function (that could be exported) ?
>
> This is just syntactic sugar for references, which is why I said it
> was easy. Similarly typing is just the typing of references.
So you mean, that if we define x with let mutable x = 1, the variable
x has in fact type int ref ?
> > Furthermore, this construct would add an entirely
> > new notion to Caml: lvalues.
>
> As stated above: they are already here, object fields.
> You may think of it as a good or bad idea, but the distinction
> between it and the fact a.x behaves differently when there is a <- and
> when there is none is subtle.
Sorry, but for field mutations the syntactic construct is not
expr <- new_val
but
expr.label <- new_val
which is semantically assign_to_label (expr, new_val), as
expr.(i) <- new_val
is a short-hand for assign_to_vector (expr, i, new_val).
In both constructs there is no notion of left values.
I really don't know if the corresponding notion for objects needs
lvalues or not.
> But well, this was only first in my wish list because I was answering
> to a message related to that. My personal priority is much lower.
I think exactly the same: the let mutable (or var construct as we used
to call it) is desirable, but may not be worth the implementation
effort.
[...]
> > So you are already satisfied, since you can write
> >
> > ocamlc -c -I +camltk -I +camlimages ocaml_unreal_t.ml
> >
> > in the current development version!
>
> Great! I had seen the introduction of -where, but didn't catch this
> one.
> Thanks, Papa Weis !
>
> Jacques
Hey, this is your ``Santa Xavier's'' work. Thanks to him.
Cheers,
Pierre Weis
INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/
next prev parent reply other threads:[~2000-12-22 14:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-12-14 14:12 Type annotations Ohad Rodeh
2000-12-15 2:25 ` Jacques Garrigue
2000-12-21 12:50 ` Ref syntax Ohad Rodeh
2000-12-22 3:29 ` Jacques Garrigue
2000-12-22 8:45 ` Sven LUTHER
2000-12-23 0:30 ` John Prevost
2000-12-22 9:07 ` Pierre Weis
2000-12-22 9:30 ` Jacques Garrigue
2000-12-22 14:22 ` Pierre Weis [this message]
2000-12-22 19:24 ` Marcin 'Qrczak' Kowalczyk
2000-12-22 9:17 ` Pascal Brisset
2000-12-23 0:37 ` John Prevost
2000-12-22 16:40 ` Marcin 'Qrczak' Kowalczyk
2000-12-23 0:39 ` John Prevost
2000-12-25 21:58 ` Pierre Weis
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