underscore in auxiliary literals of syntax-rules about chezscheme HOT 5 OPEN

I wouldn't mind changing this if we introduce it for the non-r6rs version of syntax-rules. If you expect to use the r6rs version of syntax-rules with that srfi, that won't help.

You can always kill the special meaning of underscore by rebinding it, e.g.:

> (let ((_ 0))
    (define-syntax a
      (syntax-rules (_)
        [(_ _) 'yes]
        [(_ x) 'no]))
    (list (a _) (a 4)))
(yes no)

The same binding for underscore needs to be visible both at the definition site and at the use sites.

from chezscheme.

I would welcome changing this for the non-r6rs version.

Thanks for your reply!

from chezscheme.

I've found a similar problem with another auxiliary identifier used in the same match syntax: '..1'.
In R6RS mode I get the error:

Exception in read: ..1 symbol syntax is not allowed in #!r6rs mode at line ...

In non-R6RS mode it works without problems. Is this also something mandated by the R6RS standard (I couldn't find)? If not, it would be nice to support it.

from chezscheme.

The production for <identifier> in r6rs section 4.2.1 does not admit sequences of characters starting with a period except for the "peculiar identifier" ....

from chezscheme.

Indeed. Thanks for pointing me to the right place!

from chezscheme.