Thanks for quick answers, Jean and David! The function "ly:music-deep-copy"
is the solution I was looking for :-)
> module-ref and module-set! are useful for dealing with variables of which
the name is not known in advance.
Actually, in my case I don't know in advance the name of a variable which
value I want to copy, that's why I used the module-ref function. In the
example presented to you I used a symbol, because I wanted to keep the
example as simple as possible.
> It assumes that the #{ c' des' #} part comes from something
programmatically,
Yes, that's the reason.
> The other way is to use ly:music-deep-copy and it's not like this isn't
mentioned in the "LilyPond — Extending" guide of LilyPond
You know, David, I just got lost. I wish I had more time to work with my
project.
Many many thanks!
Robert
sob., 16 paź 2021 o 12:14 David Kastrup <d...@gnu.org> napisał(a):
> Robert Kubosz <kubosz.rob...@gmail.com> writes:
>
> > I want to make a copy of a variable defined in a separate file, but run
> in
> > the same current-module.
> > The copy I make is a copy-by-reference, and in result any modifications I
> > apply to the copy also appear in the original.
> > How do I make a copy-by-value in a current-module?
> >
> > More detailed example is attached to this email.
> >
> > Thanks in advance!
> > Robert
>
> Well, one thing to note is that LilyPond's "contract" is that you only
> work with copies of music. That is why something like
>
> \trumpet-first
>
> actually delivers a _copy_ of trumpet-first rather than the original.
> Commands like \transpose then feel free to change their input as it is
> either a mere copy or does not exist elsewhere under a different name.
>
> So when you do Scheme programming, you need to work with copies. The
> easiest way, of course, is not to access variables directly but only
> write music functions processing their input.
>
> Since you can deliver this input in LilyPond mainly using \... it
> automatically is either a copy or an original expression not used
> elsewhere.
>
> The other way is to use ly:music-deep-copy and it's not like this isn't
> mentioned in the "LilyPond — Extending" guide of LilyPond.
>
> --
> David Kastrup
>
