Re: Question about Scheme's syntax

[David Kastrup]

Paolo Prete <paolopr976@gmail.com> writes:

>> On Wed, Sep 4, 2024 at 9:56 PM David Kastrup <dak@gnu.org> wrote:
>>
>>> Paolo Prete <paolopr976@gmail.com> writes:
>>>
>>> > Hello,
>>> >
>>> > Given:
>>> >
>>> > floating-markup = #(define-scheme-function (parser location x y obj)
>>> > (number? number? scheme?)
>>> >                                   #{
>>> >                                     \markup \with-dimensions #'(0 . 0)
>>> #'(0
>>> > . 0){
>>> >                                       \override #'(baseline-skip . 0)
>>> >                                       \translate #(cons x y)
>>> >                                       #obj
>>> >                                     }
>>> >                                   #})
>>>
>>> That makes no sense at all.  Obviously #obj cannot be anything but a
>>> markup here but you declare it as scheme? which just asks for obscure
>>> runtime errors.  Then there is no point in not using a markup command
>>> here in the first place.
>>>
>>> >
>>> > I can invoke it with:
>>> >
>>> > \floating-markup 15 -60 "some string"
>>> >
>>> > But how can I pass to the same function the following expression: { 
>>> > \circle
>>> > 5 } as #obj?
>>>
>>> { \circle 5 } is not a LilyPond expression.  It is a fragment of markup.
>>> You can turn it into a LilyPond expression by writing
>>>
>>> \markup { \circle 5 }
>>>
>>> in which case you'll get out an actual markup.  Outside of markup,
>>> \circle is not defined.
>>>
>>> > Something like (pseudo-syntax) :
>>> >
>>> > \floating-markup 15 -60 #{ \circle 5 #}
>>>
>>> #{ ... #} is a Scheme construct, not a LilyPond expression.  It is used
>>> for using LilyPond syntax inside of a Scheme expression.
>>>
>>> If you want to use it (in Scheme!) for writing in markup syntax, again
>>> you need to enter markup mode by writing
>>>
>>> #{ \markup ... #}
>>>
>>> in a Scheme expression.  If you are in LilyPond entry mode, you can just
>> write \markup ... instead.
>>
>
> I see but the problem remains.

That may be because you are not heeding any of my advice.

> I would like to found a way to pass a more structured object to that
> function, not only a string:
>
> %%%%%%%%%%%%%%%%%%
> \version "2.24.1"
>
> floating-markup = #(define-scheme-function (parser location x y obj)
> (number? number? scheme?)

Still scheme? instead of markup?

Still a scheme function instead of a markup command.

>                                   #{
>                                     \markup \with-dimensions #'(0 . 0) #'(0
> . 0){
>                                       \override #'(baseline-skip . 0)
>                                       \translate #(cons x y)
>                                       #obj
>                                     }
>                                   #})
>
>
> % GOOD
> \floating-markup 15 -60 "some string"
>
> % ERROR
> \floating-markup 15 -60 #{ \markup { \circle 1 } #}

I made a number of points.  Your "I see" only addressed a single one.

To wit, you are still putting a Scheme expression instead of a LilyPond
expression in a place only admitting LilyPond syntax.

The straightforward way of calling this as-is would be

\floating-markup 15 -60 \markup \circle #1

If you instead defined it as a markup command as suggested, you could
call it _inside_ of markup as, say,

\markup { ... \floating #15 #-60 \circle #1 ... }

which would be the preferable way.

-- 
David Kastrup