[antlr-interest] Anyone has a LISP ANTLR3 grammar and can con tribute it to Drools?

[Edson Tirelli]

   Thank you all for the tips.

   We will look into following your suggestions!

    Cheers,
      Edson

2008/1/24, Stuart Watt <SWatt at infobal.com>:
>
> Yes, CL is definitely the way to go.
>
> However, with Lisp, the easy stuff is:
>
> expression =
>   '(' expression* ('.' expression)? ')'
>   | symbol
>   | number
>
> which is more or less the whole "natural" syntax of Lisp - it was designed
> to be trivial parse on 1950s hardware!
>
> The language Lisp then uses "special forms" which define the semantics.
> These include examples like (if (= a b) (print c)), where "if" the
> conditional. However, special forms are not syntactic, really.
>
> However, you very quickly get into additional stuff which is done by
> "readtables", which define associations between characters, and which can
> strictly (in Common Lisp) be manipulated at run-time, or even at compile
> time. These extensions are mostly simple, but a few (such as backquote)
> are
> not. Essentially, you can associate a character with a function then then
> gets called as part of the reader, which is what takes text and turns it
> into a Lisp internal representation.
>
> In ANTLR terms, these character associations can recursively call the
> parser
> (or even the raw input stream) to do other stuff. Comments, for example,
> can
> be handled by the read-table, both the regular ";" and the balanced "#|
> ....
> |#" type.  "#" is an extension to the read-table for all sorts of nasty
> stuff, and uses the second character to invoke a function (i.e.,
> readtables
> can be cascaded). For example, "#'" is a readtable macro that reads a Lisp
> expression (as above) and conveniently wraps the (FUNCTION ...) special
> form
> around it, just as "'" is a convenience for (QUOTE ...). ANTLR can do all
> this stuff nicely with ASTs, if you put all these characters in the lexer,
> and then match them at the left of the expression rule.
>
> i.e., pick a subset of CL, or another Lisp, and when you have it, the
> grammar will probably be trivial. Don't even think about trying to do all
> of
> CL in ANTLR (or any other parser) - it was designed in a way that allows
> Lisp to take control of the input process at certain stages; ideal for
> higher-level language processing. You probably don't need some of the
> oddities of CL, like some of the rarer # readtable macros, not that they
> are
> hard to do.
>
> This is the issue with Lisp - there is a standard, but it would be
> inappropriate to implement much of it in ANTLR as it is largely dynamic
> and
> intimately connected with the core language; yet subsets may vary
> depending
> on context of use.
>
> All the best
> Stuart
>
> -----Original Message-----
> From: Ola Bini [mailto:ola.bini at gmail.com]
> Sent: Thursday, January 24, 2008 8:52 AM
> To: Edson Tirelli
> Cc: antlr-interest at antlr.org; Mark Proctor
> Subject: Re: [antlr-interest] Anyone has a LISP ANTLR3 grammar and can
> contribute it to Drools?
>
>
> Edson Tirelli wrote:
> >
> >     All,
> >
> >    We need a Lisp ANTLR3 grammar for the Drools open source project
> > (http://labs.jboss.com/drools/). We were going to build one from
> > scratch, but I was wondering if anyone has one ready and can
> > contribute to the project. All proper credits would be given, as
> > usual. Project's license is ASF.
> >    Alternatively, an (E)BNF Lisp grammar that we can use as a base to
> > build an ANTLR3 would also be helpful. Our main worry is how to define
> > the function name token for Lisp, since lisp accepts almost anything
> > as a function name.
> >
> Actually, you could make it really easy for yourself and make a lisp
> that doesn't take everything as a function name. The easiest you could
> do is probably just use the CL conventions and parse everything as
> atoms, separated by spaces. Spaces in atom names can be escaped with \.
> You can also have an atom name inside bars: |foo bar|, and then strings.
> That's really all you need.
>
> Cheers
>
> --
> Ola Bini (http://ola-bini.blogspot.com)
> JRuby Core Developer
> Developer, ThoughtWorks Studios (http://studios.thoughtworks.com)
> Practical JRuby on Rails (http://apress.com/book/view/9781590598818)
>
> "Yields falsehood when quined" yields falsehood when quined.
>
>


-- 
  Edson Tirelli
  JBoss Drools Core Development
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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