Re: Language grammar opinions
"Clive D.W. Feather" <clive@demon.net> Wed, 10 January 2007 17:25 UTC
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Date: Wed, 10 Jan 2007 16:44:20 +0000
From: "Clive D.W. Feather" <clive@demon.net>
To: Stephane Bortzmeyer <bortzmeyer@nic.fr>
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Subject: Re: Language grammar opinions
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Stephane Bortzmeyer said: >> I prefer to list the possible declaration types in the grammar, so >> would prefer the commented-out version of "declaration". > > One of the traps here is that ABNF strinsg are case-INsensitive so > this would be a problem if we switch to Unicode and it would be > inconsistent with the (current) rule that in Cosmogol, everything is > case-sensitive. I'm aware of this. Yes, it makes the ABNF look slightly nauseating, but that's a relatively small burden to bear. [One option would be to define our own extension to ABNF to specify case-sensitive strings. Um: false = !"false" ; case-sensitive I might talk to Paul Overell about it, since he's co-author of 4234 and a colleague.] >> Only after you see the next token (semicolon or comma or arrow) do >> you know if this is a declaration with an unknown type, or a >> transition. This produces a shift/reduce conflict in yacc or other >> such parser generators. > More precisely, with LR parsers like the ones generated by Yacc. LL > parsers do not have the problem. Only if you fudge around it (and the same can be done with LR parsers). >> To resolve it, I would suggest reversing the order of declarations to >> *begin* with the type: >> >> STATE : alpha, bravo, charlie ; > > Why not. It looks like C :-) A bit, yes. Combined with my proposed syntax for transitions, it means that you could make the keywords be case-insensitive if you wanted (I'm neither supporting nor opposing this) because there's no conflict. >> I see no benefit in restricting the characters in double-quoted >> names. At the very least, why allow comma and semicolon but not full >> stop and colon? > This is completely arbitrary. We should allow at least, square > brackets (RFC 2960), slashes and < and > (draft on shim6), dots, etc. Right. So why forbid anything (except " itself and possibly one escape code)? -- Clive D.W. Feather | Work: <clive@demon.net> | Tel: +44 20 8495 6138 Internet Expert | Home: <clive@davros.org> | Fax: +44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 THUS plc | | _______________________________________________ Cosmogol mailing list Cosmogol@ietf.org https://www1.ietf.org/mailman/listinfo/cosmogol
- Language grammar opinions Clive D.W. Feather
- Re: Language grammar opinions Stephane Bortzmeyer
- Re: Language grammar opinions Clive D.W. Feather