[plt-scheme] Macro changing behaviour

On Tue, Apr 21, 2009 at 10:37 PM, Matthias Felleisen
<matthias at ccs.neu.edu> wrote:
>
> This will work:
>
> #lang scheme
>
> (define-syntax-rule (test proc . args)
>  (apply proc 'args))
>
> (test (lambda () (+ 1 1)))
>
> So does this:
>
> (define-syntax-rule (test proc args ...)
>  (apply proc (list args ...)))
>
> (test (lambda () (+ 1 1)))
>
> which I consider a bit more elegant. -- Matthias
>
> P.S. Oh and do use the macro stepper. It works.
>
>

Thanks for the tip, forgot about the macro stepper! :)

>
> On Apr 21, 2009, at 6:30 PM, Paulo J. Matos wrote:
>
>> Hi all,
>>
>> I have a simple issue:
>> (define-syntax-rule (test proc . args)
>>  (apply proc args))
>> (test (lambda () (+ 1 1)))
>>
>> doesn't work. Generates:
>>  #%app: missing procedure expression; probably originally (), which is
>> an illegal empty application in: (#%app)
>>
>> But this works:
>> (apply (lambda () (+ 1 1)) '())
>>
>> So, somewhere this goes wrong. Can someone explain me what's the issue?
>>
>> Cheers,
>> --
>> Paulo Jorge Matos - pocmatos at gmail.com
>> Webpage: http://www.personal.soton.ac.uk/pocm
>> _________________________________________________
>>  For list-related administrative tasks:
>>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
>



-- 
Paulo Jorge Matos - pocmatos at gmail.com
Webpage: http://www.personal.soton.ac.uk/pocm