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Re: TimeSignature with note in denominator

From: Aaron Hill
Subject: Re: TimeSignature with note in denominator
Date: Fri, 12 Nov 2021 17:21:32 -0800
User-agent: Roundcube Webmail/1.4.9

On 2021-11-12 5:03 pm, David Kastrup wrote:
Kieren MacMillan <> writes:
At that point, the only issue is to turn

    \time #'(4 . "4.")

into an number num and a *duration* (not number) denom… which again
doesn’t required parser-fiddling, correct?

Utterly incorrect.  #'(4 . "4.") does not consult the LilyPond parser
beyond the # and there is absolutely nothing that would magically turn
"4." into a duration.  Nor should there be in my book.

Yeah, at this point, you'd have to manually write:

\time #'(4 . #{ 4. #})

And that's pretty ugly... so you might write a helper function:

foo = #(define-scheme-function
 (numer denom) (number? ly:duration?)
 (cons numer denom))

\time \foo 4 4.

It's a little better; but with proper parser support, a number-duration fraction format would be best:

\time 4/4.

That does presume, though, that TimeSignatureMusic would be refactored to support a non-numeric denominator. At the moment, it requires numbers. You could try to convert durations to numbers...

timeFraction =
  (scalar duration)
  (number? ly:duration?)
  (let* ((moment (ly:duration-length duration))
         (numerator (ly:moment-main-numerator moment))
         (denominator (ly:moment-main-denominator moment)))
   (cons (* scalar numerator) denominator)))

\fixed c' {
  | \time \timeFraction 3 4. b4. a g
  | \time \timeFraction 2 2. b2 a4 g2 a4

...but this conversion is inherently lossy. The stencil procedure would have no idea what the original rhythmic denominator was.

-- Aaron Hill

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