Re: Basic Scheme Markdown Function

[David Kastrup]

Mark Knoop <mark@opus11.net> writes:

> At 14:40 on 06 Dec 2024, Steph Phillips wrote:
>> Hi all, this one's probably a simple solution, but I'm a
>> little fuzzy on how to implement custom Scheme functions
>> still.
>
>> I'm working on a musical theater score, and there are lots
>> of instrument changes formatted like this:
>
>> changeBbClar = ^\markup {
>>     \general-align #X #-0.7
>>     \bold
>>     \override #'(box-padding . 0.5) \box
>>     "Bb Clarinet"
>> }
>
>> My end goal is a function where I can define the name of
>> the instrument and the x-alignment - something like
>
>> \InstrumentChange "Bb Clarinet" #-0.7
>
> This will do what you want.
>
> InstrumentChange =
> #(define-music-function
>   (mkp align) (markup? number?)
>   #{
>   <>^\markup
>   \general-align #X #align
>   \bold
>   \override #'(box-padding . 0.5)
>   \box #mkp
>   #})
>
> For more details about writing music functions, see this excellent
> guide put together by Jean:
>
> https://extending-lilypond.gitlab.io/en/extending/index.html

It would make more sense to have the markup as last argument because it
makes stacking functions on markup a lot more readable.  And there may
be a point in making the number an optional argument and providing a
default.  So that would end up more like

InstrumentChange =
#(define-music-function
  (align mkp) ((number? LEFT) markup?)
  #{
  <>^\markup
  \general-align #X #align
  \bold
  \override #'(box-padding . 0.5)
  \box #mkp
  #})

Of course the original example would not work until changing it to

\InstrumentChange #-0.7 "Bb Clarinet"

-- 
David Kastrup