Re: Getting started with music functions

[Aaron Hill]

On 2020-03-08 3:57 pm, Stephan Schöll wrote:
> It looks as if the "output" (return value) of a function can only be of
> type "music", not "score", "book" aso, which would disappoint me. Am I
> right? Or is there a way to define/change the type of the return value?

Music functions are for music.  Books and scores are not music.

Scheme functions are capable of returning arbitrary information.  
Scores, for instance, can be returned and handled properly.  Books 
cannot.

=> David K., do you know why the parser balks at such a top-level 
ly:book?

An explicit call to print-book-with-defaults can work around the issue.  
But likely better is to use a void function, wrapping up all the 
functionality in a single construct.

%%%%
\version "2.19.84"
scoreFunc = #(define-scheme-function () () #{ \score { { b'4 } } #})
bookFunc = #(define-scheme-function () () #{ \book { \scoreFunc } #})

\scoreFunc % works
%\bookFunc % does not

#(print-book-with-defaults #{ \bookFunc #})

betterBookFunc = #(define-void-function () ()
  (print-book-with-defaults #{ \book { \scoreFunc } #}))
\betterBookFunc
%%%%


-- Aaron Hill