# Subdivised beams bug

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## Subdivised beams bug

 Hi all, I found a small bug while using the automatic beaming function. http://lilypond.org/doc/v2.19/Documentation/notation/beams.html#setting-automatic-beam-behaviorSee: \relative c'' {   \set subdivideBeams = ##t   % Set beam sub-group length to an eighth note   \set baseMoment = #(ly:make-moment 1/8)   \set beatStructure = 2,2,2,2   c32[^"OK" c c c c c c c]     c32[^"OK" c r c c r c c]   c32[ c c c c^"BUG" c c] r } When the beat ends with a rest, the subdivised beam doesn't work correctly. -- Sent from: http://lilypond.1069038.n5.nabble.com/Bugs-f58488.html_______________________________________________ bug-lilypond mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/bug-lilypond
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## Re: Subdivised beams bug

 Am 06.09.18 um 20:57 schrieb foxfanfare: > When the beat ends with a rest, the subdivised beam doesn't work correctly. The result (using LilyPond 2.19.82) is exactly what I would’ve expected. I suppose your expectation is different so what did you expect? _______________________________________________ bug-lilypond mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/bug-lilypond
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## Re: Subdivised beams bug

 Malte Meyn-3 wrote > The result (using LilyPond 2.19.82) is exactly what I would’ve expected. > I suppose your expectation is different so what did you expect? The automatic subdivised beam is 16th instead of 8th. Here is the problem and what I would have expected: \relative c'' {   \set subdivideBeams = ##t   % Set beam sub-group length to an eighth note   \set baseMoment = #(ly:make-moment 1/8)   \set beatStructure = 2,2,2,2   c32[^"OK" c c c c c c c]     c32[^"OK" c r c c r c c]   c32[ c c c c^"BUG" c c] r       c32[ c c \set stemRightBeamCount = #1 c   \set stemLeftBeamCount = #1 c^"FIXED" c c] r } beams.JPG   -- Sent from: http://lilypond.1069038.n5.nabble.com/Bugs-f58488.html_______________________________________________ bug-lilypond mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/bug-lilypond
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## Re: Subdivised beams bug

 Hi foxfanfare, Am 06.09.2018 um 21:39 schrieb foxfanfare: > Malte Meyn-3 wrote >> The result (using LilyPond 2.19.82) is exactly what I would’ve expected. >> I suppose your expectation is different so what did you expect? > The automatic subdivised beam is 16th instead of 8th. Here is the problem > and what I would have expected: > > \relative c'' { >    \set subdivideBeams = ##t > >    % Set beam sub-group length to an eighth note >    \set baseMoment = #(ly:make-moment 1/8) >    \set beatStructure = 2,2,2,2 >    c32[^"OK" c c c c c c c] >   >    c32[^"OK" c r c c r c c] > >    c32[ c c c c^"BUG" c c] r >       >    c32[ c c \set stemRightBeamCount = #1 c >    \set stemLeftBeamCount = #1 c^"FIXED" c c] r > } > > beams.JPG you're right, LilyPond's behaviour is incorrect. Although I must admit it has explicitly been made to behave like this. This is because we (well, I) misunderstood the section in Gould's book (which is slightly misleading and especially lacks an example). BTW Dorico exposes the same bug, at least it did at the time when I realized it. Maybe they found the time to fix it in the meantime (but don't start talking about the other commercial "competitors", they're totally at a loss in that area ;-) ). The problem is that the matter is really complex and the existing code needs a complete rewrite. When you start looking at subdivisions in tuplets you'll see that it doesn't work properly at all (and in fact automatic beaming suffers from the same issues). I've (re-)attached a document that I compiled half a year ago investigating the problem. I *think* that it is quite thorough and correct, to the point where it stops. I couldn't finish it at the time, and I started it because I knew I wouldn't be able to go ahead and fix the issue (so there should be at least some documentation left behind). It was too complex for me to tackle (given my spare time), matters are complicated through the fact that I don't really know C++, and finally it turned out that you can't fix the beaming subdivisions on their own but have to fix LilyPond's notion of tuplets at the same time. TL;DR: it's a known issue, and there's no reasonable hope to have it fixed soon. Best Urs _______________________________________________ bug-lilypond mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/bug-lilypond beam-subdivisions.pdf (170K) Download Attachment
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## Re: Subdivised beams bug

 In reply to this post by foxfanfare Am 06.09.18 um 21:39 schrieb foxfanfare: > Malte Meyn-3 wrote >> The result (using LilyPond 2.19.82) is exactly what I would’ve expected. >> I suppose your expectation is different so what did you expect? > > The automatic subdivised beam is 16th instead of 8th. Ok, now after a closer look I see that the problem is not *where* the beams are subdivided but *how*. That’s a bug, yes, see Urs’s reply. _______________________________________________ bug-lilypond mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/bug-lilypond
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## Re: Subdivised beams bug

 In reply to this post by Urs Liska-3 Hello On 06/09/18 21:28, Urs Liska wrote: > TL;DR: it's a known issue, and there's no reasonable hope to have it > fixed soon. > > Best > Urs Does that mean there is a tracker for this, or do we need a new one created? James _______________________________________________ bug-lilypond mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/bug-lilypond