Re: substitution function variable name

[Jean Abou Samra]

Le 22/01/2023 à 18:22, Darren Ng a écrit :
> Thanks. The following works:
>
>    accOne =
>    #(define-music-function
>        (x        )
>        (ly:pitch?)
>      #{
>        $x 8 $x 8
>      #})
>
> My ultimate goal is a function which does the following
>
>    accTwo =
>    #(define-music-function
>        (x        )
>        (ly:pitch?)
>      #{
>        $x 8             r8
>        <($x+4) ($x+7)>8 r8
>        ($x-5) 8         r8
>        <($x+4) ($x+7)>8 r8
>      #})
>
> E.g.
>
>    \accTwo c expands to { c8r8 <eg>8r8  g,8r8 <eg>8r8 }
>    \accTwo f expands to { f8r8 <ac'>8r8 c8r8  <ac'>8r8 }
>
> What material should I read so that I'll be able to achieve this?


Spoiler: you can do that with just

\version "2.24.0"

accTwo =
#(define-music-function
    (x        )
    (ly:pitch?)
  #{
    $x 8
    r8
    <\transpose c e $x \transpose c g $x >8
    r8
    <\transpose c g, $x >8 r8
    <\transpose c e $x \transpose c g $x >8
    r8
  #})

\accTwo c'



Now, if you still want to learn how you might have done that in Scheme, 
try reading

https://extending-lilypond.readthedocs.io/en/latest/music.html#pitches

and you might also want a Scheme tutorial in case you don't already know the
language itself:

https://scheme-book.readthedocs.io/

or

https://tutoriel-scheme.readthedocs.io/

Jean

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