Backus Naur Form

skyknight has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Backus Naur Form by kvale (Monsignor) on Apr 26, 2005 at 23:19 UTC
If you have a grammar for your BNF rules, you could use Parse::RecDescent to parse the BNF rules for you. Decide on a 'nice structure' that you would like to compile the BNF rules into, and write Parse::RecDescent rules to create that structure as Parse::RecDescent parses your BNF rules. -Mark	[reply]
Re^2: Backus Naur Form by merlyn (Sage) on Apr 27, 2005 at 00:13 UTC
In fact, the language that my "spew" language uses is very close to a BNF-style language anyway. You could probably use that parser as a good start. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re^2: Backus Naur Form by spurperl (Priest) on Apr 27, 2005 at 05:13 UTC
P::RD (Parse::RecDescent) uses BNF to parse text. It doesn't parse BNF. If I understood the OP correctly, he wants to parse the BNF notation itself, i.e. given a file with a BNF description, create a parse tree from it. Naturally, you can use P::RD it to either: Look into its source and see how it parses the BNF. Write a grammar for BNF in it I recommend the second technique, because it's (1) very simple, the BNF notation is trivial. (2) Will let one understand BNF as the rule descriptions of P::RD are written in it.	[reply]
Re^3: Backus Naur Form by castaway (Parson) on Apr 27, 2005 at 08:26 UTC
P::RD doesnt quite use BNF, in fact its kind of a slightly mutated ExtendedBNF (EBNF). BNF itself is a lot simpler. C.	[reply]
Re: Backus Naur Form by castaway (Parson) on Apr 27, 2005 at 09:11 UTC
I spent quite a while also looking for a BNF parser, and turned up a couple not on CPAN (eg this one) .. But I don't remember if I got around to actually trying it out. I also found it strange that theres none on CPAN, I guess people don't do this too often.. (I was looking to parse the SQL92 spec, which is freely available in BNF form..) In the end though, I acquired the SQL1999 spec in pdf form, and hand parsed the interesting bits.. C.	[reply]
Re^2: Backus Naur Form by skyknight (Hermit) on Apr 27, 2005 at 11:58 UTC
Well, in that case, perhaps it's worth writing one. Er, maybe... I wonder if anyone other than the two of us would use it. :-)	[reply]
Re^3: Backus Naur Form by polypompholyx (Chaplain) on Apr 28, 2005 at 08:56 UTC
I would! I thought of writing a (E)BNF to P::RD parser in P::RD, but never quite got round to it. It would certainly be useful, as you can dig out BNFs for lots of languages that don't necessarily have P::RD-based parsers on CPAN. It would also make P::RD parsers hand-converted from changeable BNFs much easier to maintain. I would think it'd be quite simple to do this if you can write a meta-grammar for BNF in P::RD. Maybe it's so simple that it's been done several times already, but never made its way onto CPAN...	[reply]


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