Re: [Denemo-devel] Barlines, repeats and voltas

[Richard Shann]

On Wed, 2015-05-06 at 06:55 +0200, Éloi Rivard wrote:
> 
[...]
> 
> 
> I thinked a bit, and that sounds very weird to me. My believe is that
> scripts languages should be there to handle features for very ad-hoc
> cases.
One persons ad-hoc case is another's daily use. Music typesetting is a
vast territory most of which is of no interest to any one user, but only
a little is of interest to a large number of users. There are an
enormous number of programs for creating music notation that have set
off hard-coding everything that anyone wanted and ended up dead in the
water.

>  But coding new features with a script language, without having any
> control on it with the native language, well I think it is a very
> strange design. If think I encounter difficulties with my importer
> because a lot of things needs to be done with scheme,
they don't *have* to be done in scheme, there are underlying primitives
to create Denemo Directives from C, but it would be a nightmare to use
them.
>  and paradoxally it lacks some "scriptability".

well, that would be a paradox if it were true. But, of course, it isn't,
as you can modify and fill-out any missing features in any script,
without asking the developers to create a new binary for you.
> 
> For example the OpenFirstTimeBar command works well, but what if I
> want to open the second time barline, or the third, or the first and
> second, or the Xth ?

You invoke the command OpenNthTimeBar with suitable parameters. Looking
at the script it would seem that it hasn't been scripted to take an
arbitrary text (only to get one interactively), but it could be -
something like
(d-OpenNthTimeBar "(list (cons 'text \"3rd time\")))

then the script would process the params as it does the data field in
the case where an Nth time bar is being edited. (That would be the
elegant solution, a dirty method would be simply to make the script
expect some nth time text as a parameter following some ad hoc
prescription, but the use of alists for parameters to scripts is
something that I'm doing with all new scripted commands).

> Currently for instance, how to parse every objects in the score to
> create an exporter for instance, since there are a lot that are
> lilypond directives inserted with some scheme code ?

To create an Exporter you would look at the tag of the lilypond
directive and decide what it is for - such an exporter would be best
written in Scheme as a script as it would be easier to maintain
consistency between the scripts on the use of the tags. Of course,
people are entitled to write any LilyPond syntax they wish into a Denemo
file, and there is no way that an exporter could be written that would
be able to interpret what consequence that bit of syntax has for the
music and then to find constructs in the output language to express it. 

Really, though, the bottom line is that there is no-one writing new
hard-coded primitives in C for Denemo, the lack of a good api would make
it soul-destroying to try. All we would end up is a bug-ridden program
that no-one could fix. But there are people writing little Scheme
scripts that do useful tasks, even starting with no experience of
Scheme.

Richard