From: Andrew Green <ndrw_grn@...>
Date: 2007-04-25T02:06:07+09:00
Subject: Re: Arrow operator with dash instead of equals (->)

El mi�, 25-04-2007 a las 00:04 +0900, Martin DeMello escribi�:
> Rather than leaving the |{}| blocks entirely alone, you could
> preprocess them to change the -> to something ruby will accept, and
> then run the interpreter over the preprocessed string. Won't be a
> trivial task, but should be easier than any of the alternatives. 


El mar, 24-04-2007 a las 17:48 +0900, Brian Candler escribi�:
> On Tue, Apr 24, 2007 at 06:52:14AM +0900, Andrew Green wrote:
> > Anyway, all of this is processed by our own interpreter, including, for
> > example, the rule
> > 
> >         has_parent->place_of_birth
> > 
> > As you can see it's mainly declarative. However this part
> > 
> >         |{ (ROOT->has_given_names).textBPV + " " + (ROOT->has_last_names).textBPV }|
> >         
> > is read by our interpreter only as a string between a |{ and a }| .
> > 
> > That string is then passed to the Ruby interpreter and is meant to be
> > run (from within a specific context that our interpreter determines). In
> > these bits we don't want just our language running about, of course, we
> > want full-blown Ruby code with extensions that allow a programmer to
> > refer to the graph traversal rules using a syntax similar to that used
> > in the rule definitions that appear _outside_ the Ruby code blocks.
> 
> And my suggestion still stands: if what you want to appear inside {..} is a
> language which has -> as an operator, then a 'clean' (albeit heavyweight)
> option is to write your own expression parser using an LALR parser
> generator.
> 
> The expression parser can build a syntax tree, and then you can either walk
> this tree yourself, or use it to generate Ruby code as its output, which you
> can then run.

OK. Everything seems to indicate this is the way to go, in the
long-to-medium term. Thanks, Brian, Martin and everyone else, for all
your help.

Andrew