* [Caml-list] Bug or feature?
@ 2003-03-06 23:18 Alessandro Baretta
2003-03-06 23:43 ` Remi Vanicat
0 siblings, 1 reply; 6+ messages in thread
From: Alessandro Baretta @ 2003-03-06 23:18 UTC (permalink / raw)
To: Ocaml, Caml bugs
I'm not sure whether this is a bug or a feature.
I need to save the state of the Xcaml session between CGI
executions. Thinking in terms of Jserv-compliant
implementation, i used a Weak.Make(...).t hashtable to store
session data, so that old and no longer used data might be
automatically reclaimed by the GC. However, I found that
this implementation is buggy, because when I marshal and
unmarshal the weak hashtable, I always get an empty
hashtable back. Why is this?
I made a switch to Hashtbl.Make(...).t and now the session
handling in Xcaml works fine, except that there is no
automatic garbage collection. All other code, except for
minor modifications due to incompatibilities between the
output signatures of Hashtbl.Make and Weak.Make, has been
left untouched.
One more remark concerning the Weak.Make functor. Why in the
world are Hashtbl.Make and Weak.Make incompatible? It is
only natural to think of the second as a particularly clever
implementation of the first. Besides, the two modules are so
similar that really deserve to have the same signatures. I
strongly encourage the Caml Masters to think this over. Of
course, I could reimplement the Weak.Make functor in a Weak2
module for the ocamllib-addons package, but is it worth it?
Alex
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Caml-list] Bug or feature?
2003-03-06 23:18 [Caml-list] Bug or feature? Alessandro Baretta
@ 2003-03-06 23:43 ` Remi Vanicat
2003-03-06 23:56 ` Alessandro Baretta
0 siblings, 1 reply; 6+ messages in thread
From: Remi Vanicat @ 2003-03-06 23:43 UTC (permalink / raw)
To: caml-list
Alessandro Baretta <alex@baretta.com> writes:
[...]
> One more remark concerning the Weak.Make functor. Why in the world are
> Hashtbl.Make and Weak.Make incompatible? It is only natural to think
> of the second as a particularly clever implementation of the
> first. Besides, the two modules are so similar that really deserve to
> have the same signatures. I strongly encourage the Caml Masters to
> think this over. Of course, I could reimplement the Weak.Make functor
> in a Weak2 module for the ocamllib-addons package, but is it worth
> it?
You might be interested by my hweak library
(http://aspellfr.free.fr/hweak/) which have a similar interface than
regular Hashtbl.
I've not tested it with regard of marshal.
--
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Caml-list] Bug or feature?
2003-03-06 23:43 ` Remi Vanicat
@ 2003-03-06 23:56 ` Alessandro Baretta
0 siblings, 0 replies; 6+ messages in thread
From: Alessandro Baretta @ 2003-03-06 23:56 UTC (permalink / raw)
To: Ocaml
Remi Vanicat wrote:
>
> You might be interested by my hweak library
> (http://aspellfr.free.fr/hweak/) which have a similar interface than
> regular Hashtbl.
>
> I've not tested it with regard of marshal.
Thanks, I really think I need a weak replacement for the
ordinary hashtable module. I'll drop you a line to tell you
if I manage to get it to work with the Marshal module.
Alex
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Caml-list] Bug or feature?
2011-09-12 13:13 ` Jesper Louis Andersen
@ 2011-09-12 13:19 ` Philippe Wang
0 siblings, 0 replies; 6+ messages in thread
From: Philippe Wang @ 2011-09-12 13:19 UTC (permalink / raw)
To: Jesper Louis Andersen; +Cc: Andrej Bauer, caml-list
# let a = 32 ;; let b = 42 ;;
val a : int = 32
# b;;
Error: Unbound value b
Yeah... it's a little bit weird... not so great, actually. :-/
--
Philippe Wang
mail@philippewang.info
On Mon, Sep 12, 2011 at 3:13 PM, Jesper Louis Andersen
<jesper.louis.andersen@gmail.com> wrote:
> On Mon, Sep 12, 2011 at 14:56, Andrej Bauer <andrej.bauer@andrej.com> wrote:
>> Would anyone wish to comment on this particular "feature" of toplevel?
>>
>>
>> Objective Caml version 3.12.1
>>
>> # let a = 12 ;; I CAN PUT ANY GARBAGE HERE AND IT GETS IGNORED
>> val a : int = 12
>>
>
> It is a bug when you want to enter multiple statements, like in:
>
> # let a = 12;; a + 30;;
> val a : int = 12
>
> But it is a feature when you want to use the toplevel as a way to
> comment on what you are doing
>
> # let prod x = List.fold_left (fun x y -> x*y) 1 x;; DEAR STUDENTS,
> USE THIS DEFINITION TO DEFINE THE FACTORIAL FUNCTION
>
> where the helpful feature of the top level makes it easier for the
> student to just paste the whole line into the top level (except for
> the # at the beginning, you can't have everything, can you?).
>
> To conclude: It is a bug and a feature at the same time. Which is
> quite peculiar, since it does not have mutual exclusivity in this case
> (contrast to evaluation order where there is a right and a wrong one,
> your mileage may vary - but you can't have both at the same time for
> the same expression, though you can have both at different times for
> the same expression :).
>
> --
> J.
>
>
> --
> Caml-list mailing list. Subscription management and archives:
> https://sympa-roc.inria.fr/wws/info/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Caml-list] Bug or feature?
2011-09-12 12:56 Andrej Bauer
@ 2011-09-12 13:13 ` Jesper Louis Andersen
2011-09-12 13:19 ` Philippe Wang
0 siblings, 1 reply; 6+ messages in thread
From: Jesper Louis Andersen @ 2011-09-12 13:13 UTC (permalink / raw)
To: Andrej Bauer; +Cc: caml-list
On Mon, Sep 12, 2011 at 14:56, Andrej Bauer <andrej.bauer@andrej.com> wrote:
> Would anyone wish to comment on this particular "feature" of toplevel?
>
>
> Objective Caml version 3.12.1
>
> # let a = 12 ;; I CAN PUT ANY GARBAGE HERE AND IT GETS IGNORED
> val a : int = 12
>
It is a bug when you want to enter multiple statements, like in:
# let a = 12;; a + 30;;
val a : int = 12
But it is a feature when you want to use the toplevel as a way to
comment on what you are doing
# let prod x = List.fold_left (fun x y -> x*y) 1 x;; DEAR STUDENTS,
USE THIS DEFINITION TO DEFINE THE FACTORIAL FUNCTION
where the helpful feature of the top level makes it easier for the
student to just paste the whole line into the top level (except for
the # at the beginning, you can't have everything, can you?).
To conclude: It is a bug and a feature at the same time. Which is
quite peculiar, since it does not have mutual exclusivity in this case
(contrast to evaluation order where there is a right and a wrong one,
your mileage may vary - but you can't have both at the same time for
the same expression, though you can have both at different times for
the same expression :).
--
J.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Caml-list] Bug or feature?
@ 2011-09-12 12:56 Andrej Bauer
2011-09-12 13:13 ` Jesper Louis Andersen
0 siblings, 1 reply; 6+ messages in thread
From: Andrej Bauer @ 2011-09-12 12:56 UTC (permalink / raw)
To: caml-list
Would anyone wish to comment on this particular "feature" of toplevel?
Objective Caml version 3.12.1
# let a = 12 ;; I CAN PUT ANY GARBAGE HERE AND IT GETS IGNORED
val a : int = 12
With kind regards,
Andrej
^ permalink raw reply [flat|nested] 6+ messages in thread
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2003-03-06 23:18 [Caml-list] Bug or feature? Alessandro Baretta
2003-03-06 23:43 ` Remi Vanicat
2003-03-06 23:56 ` Alessandro Baretta
2011-09-12 12:56 Andrej Bauer
2011-09-12 13:13 ` Jesper Louis Andersen
2011-09-12 13:19 ` Philippe Wang
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