RE: functions in \with

[Trevor Daniels]

> On Tuesday 29 August 2006 10:47, Erik Sandberg replied:
Thanks for responding, Erik

> On Monday 28 August 2006 13:55, Trevor Daniels wrote:
> > I'm happily creating and using music functions but so far my attempts to
> > define functions that can be used in \with or \context clauses
> have failed.
> > The suggested technique of making a void function using (make-music
> > 'SequentialMusic 'void #t) doesn't seem to help.
>
> What do you want to achieve, more precisely?

Being relatively new to lilypond I wanted to encapsulate useful expressions
in variables and functions as I came across them.  For music-related
expressions I find these very useful, and I wanted to do the same for other
types of sequences.  Here's a simple example (thanks, Kieren) to reduce the
size of a piano grand staff which I've failed to recast as a more general
function for use in a \with clause:

\new PianoStaff  \with {
 fontSize = #-2 % reduce size of all fonts
 \override StaffSymbol #'staff-space = #(magstep -2)    % reduce size of staves
by same amount
 \override VerticalAlignment #'forced-distance = #11    % increase distance
between staves for piano dynamics
}
 ... rest of staves and music

I wanted to define a void function something like

staffSize=#(
 define-music-function (parser location fontsize separation) (number?
number?) #{
  fontSize = #$fontsize % change size of all fonts
  \override StaffSymbol #'staff-space = #(magstep #$fontsize)   % change size
of staves by same amount
  \override VerticalAlignment #'forced-distance = #$separation  % change
distance between staves for piano dynamics
 #}
 (make-music 'SequentialMusic 'void #t)
)

which could be used as:

\new PianoStaff \with { \staffSize #-2.0 #11.0 }

but attempts to use a function within \with {...} cause an 'unexpected
MUSIC_FUNCTION_SCM' error on \staffSize or leave the parser forlornly
'Parsing ...', depending on the contents of the function definition.

Using a variable without parametrisation gives an 'unexpected
MUSIC_IDENTIFIER' error.

I don't know whether it is possible to do this, or whether I simply haven't
learned how to do it properly yet.

> Note that \with uses a different lexical mode than music, so e.g. the
> \override keyword does not produce a music expression when used
> inside \with.

I had hoped (make-music 'SequentialMusic 'void #t) would prevent the parser
looking for music.
>
> You can probably perform operations on the whole \with block if you are
> clever, by applying a funciton on the \new expression, like
> \myFun \new Staff=foo \with {bla bla} {music}
>
As a relative newbie I don't have the confidence to try this yet - maybe one
day!
> --
> Erik
>
Trevor

>
>