Re: [Scheme-reports] Symbol escapes - clarification

[John Cowan <cowan@x>]

Peter Bex scripsit:

> Yeah, # is pretty special.  The spec should probably leave that
> unspecified.

So it is.

> Maybe a whitelist of characters that are definitely allowed
> in symbols?

There is such a list (of ASCII characters only) in 2.1.

> Several (most?) schemes actually try to read until the next
> s-expression separator and convert it to a number. If that fails, it's
> a symbol and taken as-is.  I'm not sure this behaviour should be
> standardized as it's very "loose" and poorly defined.

The R7RS-draft behavior is that a sequence of letters, numbers, specified
ASCII symbols, and non-ASCII characters in certain general categories
is an identifier, *provided* it does not have a prefix which is a number.
This is easy to state verbally, but makes for a messy BNF.

-- 
Henry S. Thompson said, / "Syntactic, structural,               John Cowan
Value constraints we / Express on the fly."                 cowan@x
Simon St. Laurent: "Your / Incomprehensible     http://www.ccil.org/~cowan
Abracadabralike / schemas must die!"

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