defmacro* usage

defmacro* usage

[Thierry Volpiatto]

Hi all,
I have an error with following recipe:

#+BEGIN_SRC lisp
(defmacro* test1 (&key (lang 'french))
  `(case ,lang
     (french (message "Bonjour"))
     (english (message "Hello"))))

(test1 :lang 'french)
"Bonjour"
(test1 :lang 'english)
"Hello"
(test1)
Debugger entered--Lisp error: (void-variable french)
  (eql french (quote french))
  (cond ((eql french (quote french)) (message "Bonjour")) ((eql french (quote english)) (message "Hello")))
  (case french (french (message "Bonjour")) (english (message "Hello")))
  (test1)
  eval((test1) nil)
  eval-last-sexp-1(t)
  eval-last-sexp(t)
  eval-print-last-sexp()
  call-interactively(eval-print-last-sexp nil nil)


(defun* test2 (&key (lang 'french))
  (case lang
     (french (message "Bonjour"))
     (english (message "Hello"))))

(test2 :lang 'french)
"Bonjour"
(test2 :lang 'english)
"Hello"
(test2)
"Bonjour"

#+END_SRC

As you can see, the quoted default argument 'french cause an error with
the defmacro* and work fine with the defun*.

Is it a bug or i misunderstand something?
Thanks.

-- 
  Thierry
Get my Gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 59F29997 

Re: defmacro* usage

[Andreas Schwab]

Thierry Volpiatto <thierry.volpiatto@gmail.com> writes:

> Is it a bug or i misunderstand something?

That appears to be how it works in CL.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: defmacro* usage

[Stefan Monnier]

> I have an error with following recipe:

> #+BEGIN_SRC lisp
> (defmacro* test1 (&key (lang 'french))
>   `(case ,lang
>      (french (message "Bonjour"))
>      (english (message "Hello"))))
[...]
> As you can see, the quoted default argument 'french cause an error with
> the defmacro* and work fine with the defun*.

The error is not from defmacro* but from the code you generated using defmacro*.

> Is it a bug or i misunderstand something?

A misunderstanding.  Think harder about what your macro does.  E.g. try
(macroexpand '(test1 :lang 'toto)) and (macroexpand '(test1)).
During macroexpansion, your `lang' is not supposed to hold a "language
value" but "a Lisp expression that will evaluate to a language value".


        Stefan

Re: defmacro* usage

[Thierry Volpiatto]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>> I have an error with following recipe:
>
>> #+BEGIN_SRC lisp
>> (defmacro* test1 (&key (lang 'french))
>>   `(case ,lang
>>      (french (message "Bonjour"))
>>      (english (message "Hello"))))
> [...]
>> As you can see, the quoted default argument 'french cause an error with
>> the defmacro* and work fine with the defun*.
>
> The error is not from defmacro* but from the code you generated using defmacro*.
>
>> Is it a bug or i misunderstand something?
>
> A misunderstanding.  Think harder about what your macro does.  E.g. try
> (macroexpand '(test1 :lang 'toto)) and (macroexpand '(test1)).
> During macroexpansion, your `lang' is not supposed to hold a "language
> value" but "a Lisp expression that will evaluate to a language value".
Ok, thanks for explanation.

-- 
  Thierry
Get my Gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 59F29997