On 5/17/23 16:30, Valentin Petzel wrote:
Also gotta say that this is most likely not a good thing to do. Changing
global scope variables like that can lead to confusing behaviour. Maybe if you
can elaborate on what you want to achieve we might find a more ideomatic way to
get there.
Am Mittwoch, 17. Mai 2023, 22:24:54 CEST schrieb Valentin Petzel:
Hello David,
there is some confusing going on here about how certain things are
evaluated. When you do
{ ... something ... }
this is evaluated pretty much as it is parsed, returning some music object.
So
\keepWithTag #'textI \tag #'textII { #(define l "B") }
this will first evaluate the expression { #(define l "B") } which returns an
empty music object and as side effect sets a variable, then it will call
\tag upon that music, and then call \keepWithTag on that Music.
What you intend to do is in fact not possible with \tag. What you want to do
is to delay the evaluation until the point where you have the information
to make this decision. This can be done using a music function:
\version "2.24.1"
#(define l '())
musicfn =
#(define-music-function (tag) (symbol?)
#{
#(if (equal? tag 'textI) (set! l "A"))
#(if (equal? tag 'textII) (set! l "B"))
c''1^\markup\l
#(if (equal? tag 'textI) (set! l "C"))
#(if (equal? tag 'textII) (set! l "D"))
c''1^\markup\l
#})
\musicfn textI
\musicfn textII
Note that here it is necessary to first create the global binding using
#(define ...) and then use (set! ...) to change that binding.
Cheers,
Valentin
Am Mittwoch, 17. Mai 2023, 21:58:49 CEST schrieb dfro:
I want to define and change variables mid-stream in a music expression,
while also using tags. Below is an example of what I am trying; but, it
does not work.
\version "2.24.1"
\keepWithTag #'textI
%\keepWithTag #'textII
{
\tag #'textI { #(define l "A") }
\tag #'textII { #(define l "B") }
c''1 ^\markup \l
\tag #'textI { #(define l "C") }
\tag #'textII { #(define l "D") }
c''1 ^\markup \l
}
The tags are not keeping lilypond from skipping the define's that are in
\tag #'textII. Is there a way to make this work?
Is there a way to define variables using lilypond syntax inside a music
expression?
Peace,
David
Valentin,
I want to be able to create a single music expression that I use in two
staves. In that music expression I want to use custom
define-markup-command functions that behave differently based on which
staff they are in. Below is an example of what I have been doing.
I have been using global variables for variable changes that I want both
staves to use, i.e. var-I, var-II. And, I have been making a music
function for each markup function that that chooses between the staves
using tags, and then inputs additional variables that change the
behavior of the markup function, i.e. "staff-one-var", "staff-two-var".
I am wondering if there is a more elegant way to do this.
\version "2.24.1"
%Global variables
var-I = "var-I "
var-II = "var-II "
#(define-markup-command
(symbol
layout props
var staff-variable)
(markup? markup?)
(interpret-markup
layout props
#{ \markup \concat { "Symbol " #var #staff-variable } #}
)
)
symbol =
#(define-music-function
(var)
(markup?)
#{ -\tag #'staff-one ^\markup \symbol #var "staff-one-var"
-\tag #'staff-two ^\markup \symbol #var "staff-two-var"
#})
music =
{
c1 \symbol \var-I
c1 \symbol \var-II
}
<<
\new Staff = "one"
{
\keepWithTag #'staff-one
\relative c' {
\textLengthOn
\music
}
}
\new Staff = "two"
{
\keepWithTag #'staff-two
\relative c' {
\textLengthOn
\music
}
}
>>
