On Sun, Jan 13, 2013 at 4:29 AM, David A. Wheeler <[email protected]>wrote:
> I just found some issues in R7RS draft 8 section 7.1.1 > [...] > But these productions have two issues: > 1. Having <symbol element> list double-quote is pointless, since that > is already covered by "<any character other than <vertical line> or \>". > 2. More importantly, the call to <string element> creates a useless > ambiguity, because string element's <any character other than " or \> > ALSO matches almost all the same characters. > Thanks for catching this. Note that there was another issue which is that we hadn't updated the draft after removing support for raw symbol escapes outside of vertical bars. I've fixed both of these, moving the mnemonic escapes up into the identifier section so there are no forward-references from symbol syntax to strings. Note that we voted to add both hex escapes and mnemonic escapes (like \t and \n) to symbols, but said nothing about the trailing whitespace escapes, so these are left unspecified for symbols. The relevant definitions are: <identifier> : <initial> <subsequent>* | <vertical line> <symbol element>* <vertical line> | <peculiar identifier> <symbol element> : <any character other than <vertical line> or \ > | <inline hex escape> | <mnemonic escape> | \| <mnemonic escape> : \a | \b | \t | \n | \r <string> : " <string element>* " <string element> : <any character other than <doublequote> or \ > | <mnemonic escape> | \" | \\ | \ <intraline whitespace>* <line ending> \ <intraline whitespace>* | <inline hex escape> -- Alex
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