Re: Universe of syntax possibilities, ONLY to skip over non-notes/chords

[David Santamauro]

On Sat, 13 Nov 2010 07:32:06 -0700
Carl Sorensen <address@hidden> wrote:

> >> 
> >> An easier approach might be to write an engraver
> > 
> > Pardon my ignorance, but is this something like what
> > articulate.ly[1] does or are you referring to some deeper, possible
> > c++ level? E.g.,
> > 
> > \score {
> >   \unfoldRepeats \myCustomEngraver
> > }
> 
> LilyPond music exists in at least three different states.
> 
> The first state is in the form of lilypond input music expressions.
> That's what you see in the file.

ok ...

> The second state is in the form of scheme music expressions.  The job
> of the parser is to convert lilypond music expressions into scheme
> music expressions.  Most user-defined music functions are evaluated

This, I assume, is what is output with -dbackend=scm, correct?

> The third state is in the form of stream events. The scheme music is
> converted to stream events by iterators.  Iterators traverse the
> scheme music tree in musical order, and send events to translators
> (engravers and performers).  These translators create layout objects,
> including grobs.  In addition to listening to events, translators can
> acknowledge grobs. Engravers can be written in either C++ or scheme.

This is the part that interests me the most.

> 
> Jeff's original proposal was to create an alternate parser to deal
> with input music expressions.  I don't think that's a very wise thing
> to do.

I agree simply on the basis of how complicated the syntax is from a
lilypond user, i.e., input file creator, standpoint.

> Your suggestion to do something like articulate as a music function
> would also work.  I think it's a bit more work, because it requires
> one to understand and parse the whole music expression organizations
> (e.g. sequential music, simultaneous music, chords, etc.).  But it's
> certainly doable.

Well, I am just beginning to understand (or at least try) the
internals of lilypond so my comment wasn't quite a suggestion, but
nevertheless, at least I wasn't in outer space.

> 
> The nice thing about using engravers is that when you get to the
> stop_translation_timestep phase of the engraver, you have a list of
> all the grobs taking place at that timestep.  It's the easiest way I
> know of to get the music in order.

I will study the engravers ... my biggest hurdle will probably be
understanding the tightly woven Scheme with which I am quite unfamiliar.

> > Is there already a 'test' engraver that simply outputs to stdout as
> > a simple prototype 
> 
> That would probably be a good idea, but one has not yet been written.

I want to offer to do it, but I have some intense studying to do. Is
this the correct list to ask questions about this. I'm not in
inexperienced developer, just a novice with the internals of
lilypond. I just don't want to seem burdensome.

thanks

David