Re: Changes.tely updated - 2.19.x before Feb 4th 2014 (issue 60490050)

[Janek Warchoł]

2014-02-18 18:06 GMT+01:00  <address@hidden>:
> That example is disturbing since it is not really about using a function
> as an output definition, but rather about using a function as a
> _context_ definition.  You usually would not expect the above to work
> but
> \layout { indent = #0 \coloredNotes #blue }
> to fail.  But exactly that will happen.  The actual purpose is more like
> \layout {
> \some-parameterized-function-from-my-standard-include-file-generating-the-whole-layout-block
>           #first-parameter #second-parameter #third-parameter
>           possibly additional tweaking
> }

I'm not sure if this will help you, but i can show you something
closer to a real-life example: i needed this stuff for generating
custom contexts with a fuction.

IIRC, before your improvement (i.e. before issue 3793) i had to do it
like this: 
https://github.com/openlilylib/snippets/commit/012328f4caaa192f17f99a2eab7a07b41d095878
Your change should make it possible to use define-scheme-function (and
drop the "(ly:parser-define! parser '$defaultlayout #{" bit) - if i
remember correctly (haven't worked on it for some time).

See also "create custom context definitions using a scheme function"
thread on -user.


> I think that turning \coloredNotes into a context definition producer by
> just removing the \layout { and matching } without any other change
> would work fine and make a nice example.

You mean something like this?

coloredNotes =
#(define-scheme-function (parser location col)(color?)
   #{
     \layout {
       \context {
         \Staff
         \override NoteHead #'color = #col
       }
     }
   #})

\coloredNotes #blue

{ c' }

This example doesn't compile for me, i get "error: bad expression
type" (using 82bc9ad690, pretty close to current master)

Anyway, i'm sorry but i may not have more time to discuss this right now... :-(

best,
Janek