Re: Passing pitch to function

[Valentin Petzel]

Okay, I understand the problem.

Basically what’s happening is this:
You are doing

#(define instrumentsInfo
   '(
      (piccolo . ((fullName "Piccolo") (transposition #{bf'#})))
      ))

and intend it to be a shorthand for

#(define instrumentsInfo
   (list (cons 'piccolo
               (list (list 'fullName "Piccolo")
                     (list 'transposition #{ bf' #})))))

But this is not in fact equivalent. ' is a concept of scheme we call "quoting" 
which essentially tells guile to only parse or not evaluate the expression. 
Now you need to understand how #{ ... #} works: This is translated not into a 
scheme object, but a scheme function call that parses the enclosed string. 
This means that #{ ... #} can in fact be quoted, which is why your #(display 
...) output does not give you a #<Pitch bf' >, but something looking like 
this:

((@@ (lily) read-lily-expression-internal) bf' /tmp/frescobaldi-avp8mtzi/
tmpx3_nmcsq/test.ly 6 (list))

This is the actual call Lilypond makes to evaluate #{bf'#} (the bf' you see 
there is not the symbol bf', but a character string).

This means that you are not in fact passing a pitch, but an unevaluated piece 
of scheme code.

If you want to abuse quoting for this you might use quasiquoting instead:

#(define instrumentsInfo
   `(
      (piccolo . ((fullName "Piccolo") (transposition ,#{bf'#})))
      ))

Or instead use actual lists as mentioned before

#(define instrumentsInfo
   (list (cons 'piccolo
               (list (list 'fullName "Piccolo")
                     (list 'transposition #{ bf' #})))))

Cheers,
Valentin

Am Donnerstag, 15. Juni 2023, 18:45:43 CEST schrieb Pierre-Luc Gauthier:
> I've attached my notquite-MWE.
> 
> Le jeu. 15 juin 2023, à 12 h 35, Pierre-Luc Gauthier
> 
> <p.luc.gauthier@gmail.com> a écrit :
> > So sorry, you have to remove the c''% at the end… 'should have made that
> > clear.> 
> > Le jeu. 15 juin 2023, à 12 h 33, Valentin Petzel <valentin@petzel.at> a 
écrit :
> > > Hello Pierre-Luc,
> > > 
> > > It works for me if I copy and paste your code. Can you maybe attach a ly
> > > file that does not work for you?
> > > 
> > > Cheers,
> > > Valentin
> > > 
> > > Am Donnerstag, 15. Juni 2023, 18:25:37 CEST schrieb Pierre-Luc Gauthier:
> > > > What am-I doing wrong here… ☹
> > > > 
> > > > \version "2.25.6"
> > > > 
> > > > \language "english"
> > > > 
> > > > #(define instrumentsInfo
> > > > 
> > > >    '(
> > > >    
> > > >       (piccolo . ((fullName "Piccolo") (transposition #{bf'#})))
> > > >       ))
> > > > 
> > > > instrumentInfoLookup =
> > > > #(define-scheme-function
> > > > 
> > > >   (instrument info)
> > > >   (symbol? symbol?)
> > > >   (car (cdr (assq info (cdr (assq instrument instrumentsInfo))))))
> > > > 
> > > > #(display (instrumentInfoLookup 'piccolo 'fullName))
> > > > #(display (instrumentInfoLookup 'piccolo 'transposition))
> > > > 
> > > > part =
> > > > #(define-music-function
> > > > 
> > > >   (music fullName transposition)
> > > >   (ly:music? markup? ly:pitch?)
> > > >   #{
> > > >   
> > > >     \new Staff \with {
> > > >     
> > > >       shortInstrumentName = fullName
> > > >     
> > > >     } <<
> > > >     
> > > >       \transpose $transposition c'
> > > >       $music
> > > >   >>
> > > >   >>#} )
> > > > 
> > > > %\part c' "test" bf
> > > > \part c'' #(instrumentInfoLookup 'piccolo 'fullName)
> > > > c''%#(instrumentInfoLookup 'piccolo 'transposition)
> > > > 
> > > > The ly:pitch? predicate fails. Is there a way for that pitch to be
> > > > sent as a correct ly:pitch? ¿
> > > > 
> > > > Thanks for any pointers.
> > 
> > --
> > Pierre-Luc Gauthier

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