[racket-dev] Dotted syntax/parse patterns and scribble/eval

OK, thanks for the confirmation.

On Wed, Sep 21, 2011 at 2:43 PM, Ryan Culpepper <ryan at cs.utah.edu> wrote:
> That's a bug. A pattern variable should always be bound to a syntax object.
>
> Ryan
>
>
> On 09/21/2011 03:39 PM, Casey Klein wrote:
>>
>> I'm confused by the behavior of syntax/parse pattern variables that
>> come after dots. Sometimes they're bound to lists and sometimes to
>> syntax objects.
>>
>> For example, in the following example, the variable `after-ones' gets
>> bound to a list:
>>
>>    #lang racket/base
>>
>>    (require (for-syntax racket/base))
>>
>>    (begin
>>      (require (for-syntax syntax/parse))
>>
>>      (define-syntax (m stx)
>>        (syntax-parse stx
>>          [(_ 1 ... . after-ones:expr)
>>           (if (list? #'after-ones)
>>               #''list
>>               #''not-list)]))
>>
>>      (m 1 1 2 1 2 3)) ; 'list
>>
>> but it gets bound to a syntax object if I drop the variable's `expr'
>> syntax-class.
>>
>> That is, unless you're using scribble/eval, in which case dropping the
>> syntax-class does not change the behavior:
>>
>>    #lang scribble/manual
>>
>>    @(require scribble/eval)
>>
>>    @(parameterize ([current-eval (make-base-eval)])
>>       (interaction-eval (require (for-syntax racket/base)))
>>       (interaction (begin
>>                      (require (for-syntax syntax/parse))
>>
>>                      (define-syntax (m stx)
>>                        (syntax-parse stx
>>                          [(_ 1 ... . after-ones:expr)
>>                           (if (list? #'after-ones)
>>                               #''list
>>                               #''not-list)]))
>>
>>                      (m 1 1 2 1 2 3))))
>>
>> What's going on?
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>
>