[parenscript-devel] CASE keys in Parenscript vs. Lisp

[Vladimir Sedach]

Ok, I pushed a patch. Let me know if that works ok.

Vladimir

On Thu, Sep 13, 2012 at 10:52 PM, Daniel Gackle <danielgackle at gmail.com> wrote:
> Yes, that's it. Sorry for the ambiguity. I actually rely on this behavior
> in more than one place; it basically gives you #DEFINE for magic
> numbers.
>
> Thanks,
> Dan
>
>
> On Thu, Sep 13, 2012 at 7:40 PM, Vladimir Sedach <vsedach at gmail.com> wrote:
>>
>> Do you mean something like this:
>>
>> (symbol-macrolet ((x 1))
>>     (let ((blah 1))
>>      (case blah
>>        (0 3)
>>        (x 7)
>>        (t 13))))
>>
>> Where the key x is supposed to expand to 1? In CL that code evaluates
>> to 13, but since there's no way symbols can be used as keys I suppose
>> using symbol macros that expand to numbers makes a lot of sense.
>>
>> Let me know if the above example is the behavior you think should be
>> provided (ie the form should return 7), and I'll make a patch.
>>
>> Vladimir
>>
>> On Thu, Sep 13, 2012 at 10:15 PM, Daniel Gackle <danielgackle at gmail.com>
>> wrote:
>> > Trying to upgrade to the latest PS, I have a problem with this CASE fix:
>> > it rejects symbol macros that expand to numbers. It's quite handy to
>> > use symbol macros this way for compile-time constants, so I hope
>> > the desired behavior can be restored.
>> >
>> > Daniel
>> >
>> >
>> >
>> > On Mon, Sep 3, 2012 at 7:22 PM, Vladimir Sedach <vsedach at gmail.com>
>> > wrote:
>> >>
>> >> This I would definitely call a bug. Since the position PS takes right
>> >> now is that it doesn't have symbols as run-time objects, I made the
>> >> decision to disallow them as keys in CASE clauses. Only keyword
>> >> symbols (which are translated to strings), numbers and string literals
>> >> are allowed.
>> >>
>> >> The behavior exhibited in your case is perfectly ok JavaScript though,
>> >> so the SWITCH special form still supports having variables and others
>> >> things as keys.
>> >>
>> >> I made a note in the reference manual (in the repo, I'll update the
>> >> version on the PS website with the next release), and also fixed some
>> >> other bugs I found in CASE and SWITCh statements.
>> >>
>> >> Thank you for bringing this issue up!
>> >>
>> >> Vladimir
>> >>
>> >> On Mon, Sep 3, 2012 at 8:09 AM, Boris Smilga <boris.smilga at gmail.com>
>> >> wrote:
>> >> > Hello.
>> >> >
>> >> > I've noticed that Parenscript has a different semantics from Lisp as
>> >> > regards keys of CASE clauses.  Lisp assumes an implicit QUOTE in this
>> >> > context, so that a symbol used as CASE clause key matches a test-key
>> >> > which is EQL to the symbol, as opposed to its value.  Parenscript, on
>> >> > the other hand, translates CASE forms to switch statements where
>> >> > symbol keys are used as identifiers.  E. g.
>> >> >
>> >> >   (let* ((foo 'bar) (bar 'foo) (x bar))
>> >> >     (case x ((foo) 1) ((bar) 2)))
>> >> >
>> >> > translates to
>> >> >
>> >> >   (function () {
>> >> >       var foo = 'bar';
>> >> >       var bar = 'foo';
>> >> >       var x = bar;
>> >> >       switch (x) {
>> >> >       case foo:
>> >> >           return 1;
>> >> >       case bar:
>> >> >           return 2;
>> >> >       };
>> >> >   })();
>> >> >
>> >> > Note that the former evaluates to 1, the latter to 2.
>> >> >
>> >> > Now, is this a bug, or a feature?  The section on CASE in the
>> >> > Parenscript Manual is actually misleading, whatever the answer.
>> >> >
>> >> >  — B. Smilga.
>> >> >
>> >> > _______________________________________________
>> >> > parenscript-devel mailing list
>> >> > parenscript-devel at common-lisp.net
>> >> >
>> >> > http://lists.common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
>> >>
>> >> _______________________________________________
>> >> parenscript-devel mailing list
>> >> parenscript-devel at common-lisp.net
>> >> http://lists.common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
>> >
>> >
>> >
>> > _______________________________________________
>> > parenscript-devel mailing list
>> > parenscript-devel at common-lisp.net
>> > http://lists.common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
>> >
>>
>> _______________________________________________
>> parenscript-devel mailing list
>> parenscript-devel at common-lisp.net
>> http://lists.common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
>
>
>
> _______________________________________________
> parenscript-devel mailing list
> parenscript-devel at common-lisp.net
> http://lists.common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
>