Folks,
I would like to write a markup function that can either accept a
markup or a markup list as an argument. The code below works fine,
reporting
```
bar: (#<procedure flat-markup (layout props)>)
baz: 1
bar: ((#<procedure sharp-markup (layout props)>)
(#<procedure sharp-markup (layout props)>))
baz: 1
```
as expected. (The `baz` argument is inserted in the demo code to
avoid interference with LilyPond's special handling of a markup
function's last argument, which can be either a markup or a markup
list, for example, `\bold foo` or `\bold { foo bar }`.)
However, if I activate the commented-out code, LilyPond aborts with
```
error: syntax error, unexpected MARKUP_FUNCTION
\markup \fooEither
\flat #1
```
It seems to me that this is a limitation built into LilyPond's parser,
and it is not possible to do what I would like to achieve, probably
due to the above-mentioned special handling of the last argument. Has
someone more insight?
Werner
======================================================================
\version "2.24.0"
#(define-markup-command (foo layout props bar baz)
(markup? number?)
(ly:message "bar: ~a" bar)
(ly:message "baz: ~a" baz)
(interpret-markup layout props bar))
\markup \foo \flat #1
#(define-markup-command (fooList layout props bar baz)
(markup-list? number?)
(ly:message "bar: ~a" bar)
(ly:message "baz: ~a" baz)
(interpret-markup layout props (car bar)))
\markup \fooList { \sharp \sharp } #1
% #(define (markup-or-markup-list? x)
% (or (markup? x) (markup-list? x)))
%
% #(define-markup-command (fooEither layout props bar baz)
% (markup-or-markup-list? number?)
% (ly:message "bar: ~a" bar)
% (ly:message "baz: ~a" baz)
% (interpret-markup layout props (if (markup-list? bar) (car bar) bar)))
%
% \markup \fooEither \flat #1
% \markup \fooEither { \sharp \sharp } #1
