Export to pure Scheme file

[uliska]

This issue is copied over from openlilylib/snippets#138.

This is a result from discussions in the threads
http://lists.gnu.org/archive/html/lilypond-user/2015-11/msg00186.html
(and maybe also
http://lists.gnu.org/archive/html/lilypond-user/2015-11/msg00187.html).

It is necessary to add raw Scheme as an export target for annotate. This file can later be read in again and used for creating a critical report within LilyPond.
It's not clear yet whether this will be accessible in the same score, in a subsequent score, in a new bookpart or only in a separate compilation.

[jefferyshivers]

I'm interested in looking into this once the first release of the latex package is behind me.

I suspect, to process the score's annotations (which may include in-score footnotes and bottom-of-the-page footnotes, in additions to the endnotes), there might need to be some kind of multiple-pass approach (I'm not too familiar with the order in which things are engraved / processed by LP).

If Guile/LP can't/doesn't write files synchronously, we can probably tell LP to print-to-score the footnotes/annotations based on the current list as it is being processed along the way, but just as well export to a file that same list in the exact same format at the end of the process. Then the list/file can be referenced/used separately, but not necessarily depended-on by LP at the time of engraving (if told, by some option, to indeed engrave those annotations to the score).

Does that make sense / sound like I'm on the right track?

[uliska]

I'm not sure as I would have to get into the topic quite deeply, but i have the impression it makes sense.