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

From: Ryan Culpepper (ryan at cs.utah.edu)
Date: Wed Sep 21 19:44:51 EDT 2011

On 09/21/2011 04:14 PM, Neil Van Dyke wrote:
> Ryan Culpepper wrote at 09/21/2011 05:43 PM:
>> That's a bug. A pattern variable should always be bound to a syntax
>> object.
> This seems to me like a good scenario of one kind of backward
> compatibility issue affecting PLaneT.
> For example, I think that a fix to this bug would break a forthcoming
> PLaneT package of mine, as it is now. (Of course, I can add add a
> workaround now, since I know of the problem before the package went out
> the door. That wouldn't work for anyone who already released packages
> and doesn't know of the problem in advance.)

This particular bug only affects patterns of the form

   (<stuff> . var:expr)

If you've seen pattern variables get non-syntax values in some other 
way, please let me know! (BTW, by "pattern variable" I mean a name bound 
directly in the pattern; "nested attributes" like var.value are allowed 
to contain non-syntax values.)

> Perhaps automated testing of PLaneT packages against prospective Racket
> releases is part of the solution?

I'll have to let someone else answer that.

> BTW, "syntax-parse" is great stuff.



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