Re: arranger.ly and lilypond 2.21+: error with the \note markup command

[Thomas Morley]

Am Fr., 15. Jan. 2021 um 23:26 Uhr schrieb Stefano Troncaro
<stefanotroncaro@gmail.com>:
>
> Hi everyone,
>
> I started learning to use the spectacular arranger.ly library that was 
> mentioned in the list a while ago.
>
> While most of it works great, I found that internally it sometimes uses the 
> \note markup command, that changed between versions: in 2.20 it requires an 
> argument of type string, while from 2.21 onwards it requires an argument of 
> type duration. This causes an error and makes it so that files that use 
> arranger.ly do not compile on Lilypond 2.21 onwards.
>
> I'm sure it'd be easy to patch. Is there an easy way to transform strings 
> into durations?

Iiuc, how about:

%% from define-markup-commands
#(use-modules (ice-9 regex))

#(define-public log2
  (let ((divisor (log 2)))
    (lambda (z) (inexact->exact (/ (log z) divisor)))))

#(define (parse-simple-duration duration-string)
  "Parse the `duration-string', e.g. ''4..'' or ''breve.'',
and return a (log dots) list."
  (let ((match (regexp-exec (make-regexp "(breve|longa|maxima|[0-9]+)(\\.*)")
                            duration-string)))
    (if (and match (string=? duration-string (match:substring match 0)))
        (let ((len (match:substring match 1))
              (dots (match:substring match 2)))
          (list (cond ((string=? len "breve") -1)
                      ((string=? len "longa") -2)
                      ((string=? len "maxima") -3)
                      (else (log2 (string->number len))))
                (if dots (string-length dots) 0)))
        (ly:error (_ "not a valid duration string: ~a") duration-string))))

%% and then:

#(define (string->duration strg)
  (apply ly:make-duration (parse-simple-duration strg)))

%% test
#(display-scheme-music (string->duration "16.."))

Cheers,
  Harm