Re: music function with access to context properties like currentBarNumber?

[Jan-Peter Voigt]

Hi Malte, Abraham,

if I knew how to achieve it, it would already be part of the 
edition-engraver.
The problem is, that one has to unfold the music expression during 
iteration, so he may need to build a parallel music iterator, that 
creates the needed grobs. That sounds misleading.
Another feature I'd like to add, but leads to the same problem, would be 
to add cue-notes with in a manner the edition-engraver adds overrides.

You can reach the context-properties thru apply-context, but then still 
the duration set to late, as you can see in the (not working) example 
below.

Well, this is just a quick shot, that might lead someone else to an 
answer ;)

Cheers, Jan-Peter

%%%%
% non-functional example

\version "2.18.2"

fun = #(define-music-function (parser location bars)(integer?)
         (let ((cbn 0)
               (ml (ly:make-moment 4 4))
               (rest #{ R1 #}))
           #{
             \applyContext #(lambda (context)
                              (set! cbn (ly:context-property context 
'currentBarNumber))
                              (ly:message "bar-number: ~A" cbn)
                              (set! ml (ly:context-property context 
'measureLength))
                              (ly:message "measure-length: ~A" ml)
                              (ly:music-set-property! rest 'duration ml))
             $rest
           #}
           ))

{ \time 3/4 bes'4 a' c''8 b' | \fun 3 | bes'4 a' c''8 b' }
%%%%


Am 15.07.2015 um 20:20 schrieb Malte Meyn:
> Hello list,
>
> I would like to have somthing like
>
> \version "2.19.22"
> {
>   \time 3/4
>   % bar 1
>   c'2.
>   \skipUntil #5 % s2.*4
>   % bar 5
>   c'2.
>   \restUntil #8 % R2.*2
>   % bar 8
>   c'2.
> }
>
> so I don’t have to count bars every time an instrument has a long rest 
> (could also be helpful when composing, or, in a more advanced version, 
> when skipping several bars with many time signature changes).
>
> My first thought was “I need a music function that accesses 
> currentBarNumber” but that (and, for the more advanced version, 
> measureLength) is a context property. Now I don’t know how to get the 
> context to this music function and making it return a (make-music 
> 'MultiMeasureRestMusic …). Attached is my first attempt but that 
> returns only (make-music 'ApplyContext …).
>
> Is this the correct approach? Or do I have to write an engraver? If 
> so, where can I learn how to do that?
>
> Thanks in advance,
> Malte
>
>
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