Subject: Re: Railroad diagrams, a-la sqlite
From: Hannu Krosing <hannu@krosing.net>
To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: Steve Atkins <steve@blighty.com>, pgsql-docs <pgsql-docs@postgresql.org>
In-Reply-To: <4C413FDE.4040501@enterprisedb.com>
References: <2AACFC47-C121-4549-B015-AC4FCA9380CE@blighty.com>
	<4C413FDE.4040501@enterprisedb.com>
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Date: Sat, 17 Jul 2010 10:02:42 +0300
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On Sat, 2010-07-17 at 08:30 +0300, Heikki Linnakangas wrote:
> On 17/07/10 07:33, Steve Atkins wrote:
> > Has everyone seen the "railroad diagrams" sqlite use in their docs? http://www.sqlite.org/lang_createindex.html , as one example.
> >
> > Would it be nice to have the same sort of format in the postgresql docs? (Yeah, I'm volunteering, if people think they're a useful thing, 'cos I think they'd add a lot to our documentation.)
> 
> That would be nice. It would have to be automatically generated from the 
> syntax descriptions we already have, otherwise it'd be unmaintainable. 
> Also, the text representation would have to still be there in an alt tag 
> - I note that the the sqlite docs don't have that.
> 
> Any idea how those sqlite images are generated?

I have used this:

http://www.informatik.uni-freiburg.de/~thiemann/haskell/ebnf2ps/

to make railroad diagrams from postgresql lex/yacc sources a few years
ago, when looking into adding WITH support to pg.

As it takes extended BNF as input i had to convert pg's lex+yacc into
eBNF, which IIRC I did using some python scripts + manual tweaking.


> -- 
>    Heikki Linnakangas
>    EnterpriseDB   http://www.enterprisedb.com
>