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Re: [Scheme-reports] 7.1.1 lexical structure

On Thu, May 19, 2011 at 1:58 PM, Andy Wingo <wingo@x> wrote:
> What is the deal with PECULIAR IDENTIFIER?  Is +.+ useful for someone?
> It seems an odd production, given that implementations are free to
> extend the set of valid identifiers.  The R5RS was clearer here.

The English rule is very simple:

  [...] in all implementations a sequence
  of letters, digits, and ``extended alphabetic characters'' that
  does not have a prefix which is a valid number is an identifier.

This was chosen to allow a wide range of new identifiers,
leave room for numeric extensions, and remove _all_ of
the hard-coded peculiar identifiers found in R5RS and R6RS.

Unfortunately, since BNF doesn't have "exception" rules
the actual rules are a little clumsy.


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