[Caml-list] duplicate labels

[Caml-list] duplicate labels

[Török Edwin]

Hi,

The following is accepted:

let foo ~x ~x () = ()
let () =
  foo ~x:4 ~x:5 ()

I tried -w A and I got no warnings with OCaml 4.01.0, is this intended?
Should I file a feature request to get a warning for this situation?

(How I got in this situation: I did an overly eager search/replace that caused the duplicate ~x)

Best regards,
--Edwin

Re: [Caml-list] duplicate labels

[Lukasz Stafiniak]

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I reported this a couple of years ago:
http://caml.inria.fr/mantis/view.php?id=4904


On Tue, Sep 17, 2013 at 2:55 PM, Török Edwin <edwin+ml-ocaml@etorok.net>wrote:

> Hi,
>
> The following is accepted:
>
> let foo ~x ~x () = ()
> let () =
>   foo ~x:4 ~x:5 ()
>
> I tried -w A and I got no warnings with OCaml 4.01.0, is this intended?
> Should I file a feature request to get a warning for this situation?
>
> (How I got in this situation: I did an overly eager search/replace that
> caused the duplicate ~x)
>
> Best regards,
> --Edwin
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

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Re: [Caml-list] duplicate labels

[Gabriel Scherer]

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I think this is also related to
  http://caml.inria.fr/mantis/view.php?id=6070

Note that enabling warning 27 (non-suspicious unused variables) also solves
this issue:

 % ocaml -w +27
        OCaml version 4.00.1

# let foo ~x ~x () = x;;
Warning 27: unused variable x.
val foo : x:'a -> x:'b -> unit -> 'b = <fun>



On Tue, Sep 17, 2013 at 2:55 PM, Török Edwin <edwin+ml-ocaml@etorok.net>wrote:

> Hi,
>
> The following is accepted:
>
> let foo ~x ~x () = ()
> let () =
>   foo ~x:4 ~x:5 ()
>
> I tried -w A and I got no warnings with OCaml 4.01.0, is this intended?
> Should I file a feature request to get a warning for this situation?
>
> (How I got in this situation: I did an overly eager search/replace that
> caused the duplicate ~x)
>
> Best regards,
> --Edwin
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

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Re: [Caml-list] duplicate labels

[Török Edwin]

On 09/17/2013 04:09 PM, Gabriel Scherer wrote:
> I think this is also related to
>   http://caml.inria.fr/mantis/view.php?id=6070
> 
> Note that enabling warning 27 (non-suspicious unused variables) also solves this issue:
> 
>  % ocaml -w +27
>         OCaml version 4.00.1
> 
> # let foo ~x ~x () = x;;
> Warning 27: unused variable x.
> val foo : x:'a -> x:'b -> unit -> 'b = <fun>

I thought that is just because I don't use x in the function, but you are right it warns even if I use x
and I have the duplicate label:

# let foo ~x ~x () = x;;        
Warning 27: unused variable x.
val foo : x:'a -> x:'b -> unit -> 'b = <fun>

I think thats good enough for me now, I'll pay more attention to the unused variable warning.

Best regards,
--Edwin

Re: [Caml-list] duplicate labels

[Goswin von Brederlow]

On Tue, Sep 17, 2013 at 04:49:51PM +0300, Török Edwin wrote:
> On 09/17/2013 04:09 PM, Gabriel Scherer wrote:
> > I think this is also related to
> >   http://caml.inria.fr/mantis/view.php?id=6070
> > 
> > Note that enabling warning 27 (non-suspicious unused variables) also solves this issue:
> > 
> >  % ocaml -w +27
> >         OCaml version 4.00.1
> > 
> > # let foo ~x ~x () = x;;
> > Warning 27: unused variable x.
> > val foo : x:'a -> x:'b -> unit -> 'b = <fun>
> 
> I thought that is just because I don't use x in the function, but you are right it warns even if I use x
> and I have the duplicate label:
> 
> # let foo ~x ~x () = x;;        
> Warning 27: unused variable x.
> val foo : x:'a -> x:'b -> unit -> 'b = <fun>
> 
> I think thats good enough for me now, I'll pay more attention to the unused variable warning.
> 
> Best regards,
> --Edwin

What about this code?

# let foo y ~x = 2 * x + y;;
val foo : int -> x:int -> int = <fun>
# let bar ~x = foo x;;
val bar : x:int -> x:int -> int = <fun>
# let x = 1;;
val x : int = 1
# bar ~x ~x;;
- : int = 3
# bar ~x:1 ~x:2;;
- : int = 5

Other than being confusing there doesn't seem to be anything wrong with
a duplicate label. It just requires you to apply the ~x in order.

MfG
	Goswin

Re: [Caml-list] duplicate labels

[Lukasz Stafiniak]

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On Thu, Sep 19, 2013 at 11:29 AM, Goswin von Brederlow <goswin-v-b@web.de>wrote:

>
> What about this code?
>
> # let foo y ~x = 2 * x + y;;
> val foo : int -> x:int -> int = <fun>
> # let bar ~x = foo x;;
> val bar : x:int -> x:int -> int = <fun>
> # let x = 1;;
> val x : int = 1
> # bar ~x ~x;;
> - : int = 3
> # bar ~x:1 ~x:2;;
> - : int = 5
>
> Other than being confusing there doesn't seem to be anything wrong with
> a duplicate label. It just requires you to apply the ~x in order.
>
> I believe it is not a type system-level feature wish, but a syntax of
definition-level feature wish.

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