Re: SCM-ification of parser

[Han-Wen Nienhuys]

Erik Sandberg schreef:
> On 5/18/06, Han-Wen Nienhuys <address@hidden> wrote:
> > Erik Sandberg schreef:
>
> > > If we use a separate module for syntax expressions, why not just say 
> > foo?
> > > e.g.:
> > > (sequential-music .. )
> > > for a syntax expression that represents (and, incidentally, produces 
> > music
> > > which represents) sequential music.
> >
> > because we already have those, and we risk compatibility breakage if we
> > use them to hook into the parser.
>
> But the other sequential-music is defined in a different module, so
> there should be no problems with namespace clashes, or?
>
> > >>    (ly:parser-set-syntax 'music-sequence my-music-sequencer)
> > >
> > > I don't understand. Why would the parser be interested in knowing 
> > which syntax
> > > functions that exist? AFAICS it should be sufficient for the parser 
> > to just
> >
> > 1. because the parser also determines which ones are called.
>
> how? According to my plan, the functions do that themselves (by being
> either macros or functions). Perhaps my plan differs from yours?

Yes, but I think it's useful to keep the connection between the 
productions in parser.yy, and the lisp code that is generated. I'm not 
yet convinced that generating a large expression and eval'ing that is a 
the best way to go through with this; it seems very unstructured. Let's 
move one step at a time.

It's a also a tad more efficient, but that's a secondary concern.

> > We could
> > use this to generate documentation for the syntax/grammar automatically
> > (something which is now done manually in the docstrings of the music
> > types).
>
> Well, that makes sense.
>
> > 2. because it would allow a user to override an individual syntax
> > production rule cleanly.
>
> OK. Why would a user want to do that?

In some cases, that's already possible now, eg. with pipeSymbol. 
Another example: we could use this mechanism for invoking all the 
different toplevel-{music,score,book}-handlers.

--

Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen

LilyPond Software Design
 -- Code for Music Notation
http://www.lilypond-design.com