From: skaller <skaller@users.sourceforge.net>
To: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
Cc: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] partial application warning unreliable?
Date: Thu, 08 Dec 2005 18:11:49 +1100 [thread overview]
Message-ID: <1134025910.8948.44.camel@rosella> (raw)
In-Reply-To: <20051208.121012.49167263.garrigue@math.nagoya-u.ac.jp>
On Thu, 2005-12-08 at 12:10 +0900, Jacques Garrigue wrote:
> From: skaller <skaller@users.sourceforge.net>
>
> > method add_nonterminal (s:string) (sr:range_srcref) (toks:
> > Flx_parse.token list) (term:ast_term_t) =
> >
> > ...
> > state#add_nonterminal tok (Flx_srcref.slift sr) t;
> >
> > Method has 4 arguments, but the call applies to only 3.
> >
> > Woops, no warning!! Bad! This error of mine caused a serious
> > bug -- the method call didn't do anything!
>
> Wait a minute, is there anything after the semicolon?
yes, it is followed by an empty list []
> The point is that a trailing semicolon at the end of a method
> definition does nothing: it still returns the result of the previous
> expression!
That's a bit weird, but I guess the decision is somewhat
arbitrary .. I actually wonder if using camlp4 changes this
result (since I guess it is an artefact of the parser/grammar
rather than a deliberate choice .. :)
> I wonder whether this behaviour is good or not, but this also means
> that there is no reason to have a warning here.
IMHO an expression on the LHS of a semicolon expression
(possibly excluding the degenerate case the RHS is empty)
should have type unit**, and it should be *hard error* not a warning
if it doesn't: the ignore(expr) function can be used
to suppress the error if required.
** as you know I think the type should be void,
not unit. Other systems (such as FISh) has a special
type such as 'command' for this. But whichever type
is chosen, Ocaml should be *strict* about it. It is
strict everywhere else .. I don't understand why it
isn't strict here.
> If there is an expression after the semicolon, and you have no
> warning, then file a bug report: the type system is supposed to detect
> all partial applications in statements, except for functions whose
> result is a polymorphic type variable.
I don't have a reduced example though, and the error is
already fixed in my code.
> By the way, your other example with classes is wrong:
>
> # class cc = object (self)
> method f x y = x + y
> method g () = self#f 1;
> end;;
> class cc :
> object method f : int -> int -> int method g : unit -> int -> int end
>
> No warning, for the reason stated above: the semicolon does nothing.
Ouch .. you're right -- I actually DID get an error F .. jumbled
up inside THREE copies of the text the top level printed trying
to underline the error. The toplevel is very sick ..
BTW: the error flags documentation is very confusing:
A/a enable/disable all warnings
X/x enable/disable all other warnings
other than what? I am using -w yz but STILL get
warning X, unused function argument .. some of this
happens in Frontc/CIL which I'm using and I would like
to minimise patches.
BTW: what is this for?
S/s enable/disable non-unit statement
Isn't that going to be F partial application 99% of the time?
If I turn off F, will I get S instead?
--
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net
next prev parent reply other threads:[~2005-12-08 7:12 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-08 2:39 skaller
2005-12-08 3:10 ` [Caml-list] " Jacques Garrigue
2005-12-08 7:11 ` skaller [this message]
2005-12-08 14:41 ` Damien Doligez
2005-12-08 23:51 ` malc
2005-12-09 1:43 ` skaller
2005-12-09 2:15 ` Jacques Garrigue
2005-12-09 2:56 ` skaller
2005-12-09 15:26 ` malc
2005-12-10 0:49 ` Jacques Garrigue
2005-12-10 1:40 ` malc
2005-12-09 12:21 ` Andreas Rossberg
2005-12-09 17:17 ` skaller
2005-12-09 17:52 ` Andrej Bauer
2005-12-09 18:54 ` Andreas Rossberg
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