Re: Need help with Scheme code

[Aaron Hill]

On 2019-12-17 4:21 pm, Paolo Prete wrote:
> Hi Stefano,
>
> unfortunately, it doesn't increment the counter globally, and the two 
> ids
> in the SVG file are identical

You will need to define a music function so that the (serial) procedure 
is called on each occurrence.  Here's an option that rolls in the 
counter logic:

%%%%
\version "2.19.83"

token = #(let* ((ctr 0) (ctr! (lambda () (set! ctr (1+ ctr)) ctr)))
  (define-music-function (mus) (ly:music?)
    (let ((id (format #f "foobar_~a" (ctr!))))
      #{ \tweak output-attributes #`((id . ,id)) #mus #})))

\relative { c'4 d8 -\token [ e ] f -\token [ g ] c,4 }
%%%%


-- Aaron Hill