Werner LEMBERG <w...@gnu.org> writes:
> Folks,
>
>
> I would like to write a markup function that can either accept a
> markup or a markup list as an argument.
You mean, a markup command.
> 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?
The documentation clearly states:
<http://lilypond.org/doc/v2.25/Documentation/extending/markup-command-definition-syntax>
Arguments are distinguished according to their type:
• a markup, corresponding to type predicate ‘markup?’;
• a list of markups, corresponding to type predicate ‘markup-list?’;
• any other scheme object, corresponding to type predicates such as
‘list?’, ‘number?’, ‘boolean?’, etc.
You use a predicate other than markup? or markup-list?, so this counts
as any other scheme object.
The real question is what you actually are trying to achieve here.
--
David Kastrup
