Re: Getting beam subdivision working

[Jason Yip]

On 2023-06-16 17:26, Carl Sorensen - carl.d.sorensen(a)gmail.com wrote:
> Before you work too hard on beam-subdivide-tuplets.ly 
> <http://beam-subdivide-tuplets.ly>, you may wish to investigate Urs's 
> comment on local beat structure for tuplets.  As far as I know now, 
> you don't have a beat structure yet implement for subbeams; that may 
> be a very powerful construct that could be helpful.
>
> I suspect that much of the concern about baseMoment and subdivision in 
> Urs's paper can actually be resolved with baseMoment and beatStructure 
> (including local beat structures).  And using baseMoment and 
> beatStructure would potentially resolve the problem of only allowing 
> 1/x subdivision discussed on page 3.
>
> You have created a Sub_beam class.  Is there a reason to use a 
> Sub_beam class instead of just creating a new Beaming_pattern element 
> as Urs suggests on page 7?  Can a Sub_beam just be a Beaming_pattern?  
> Perhaps using the same class of object would prevent duplication.

The purpose of my Subbeam class is to calculate a local baseMoment and 
beatStructure on the fly. You can see at 
https://gitlab.com/ljyip/lilypond/-/blob/e7d39a076ccf50555bfa2d352400caaf28db2678/lily/beaming-pattern.cc#L272 
. The code infrustructure to support fancy tuplet-local beatStructure's 
is already there, but the default local beatStructure is assumed to just 
be a list of /denominator/ items of value /numerator/ for now since we 
should discuss the way to support such from manual user input or 
automatically.

I originally wanted to avoid Beaming_pattern acting as the recursive 
class because it would have to make copies of Beam_rhythmic_element in 
their own vector and I thought that it could be too computationally 
expensive. Subbeam acts like a C++20 range on the vector, only storing a 
start and end index for itself. Most people won't even have nested 
tuplets anyways, so maybe Beaming_pattern can bear the computations anyways.


> P.S. Have you tried any of Urs's hard examples to see if your code 
> works on them?  It would be nice to see how many you have already 
> solved!  I suspect it's most of them.
Figure 1 code:

```lilypond

\relative a' {
  \compoundMeter #'((2 4) (5 32))
  \set baseMoment = #(ly:make-moment 1/32)
  \set beatStructure = #'(8 8 5)
  \set subdivideBeams = ##t
  \repeat unfold 16 a32
  \repeat unfold 5 a32
}

```

My extended version of Figure 4 code:

```lilypond

\relative c' {
  \time 1/4
  \set subdivideBeams = ##t
  c32 c
  \tuplet 3/2 {
    \repeat unfold 4 c64
    \tuplet 3/2 { \repeat unfold 12 c128 }
    \repeat unfold 4 c64
  }
  c32 c
  \break

  \tuplet 3/2 {
    \tuplet 3/2 { \repeat unfold 12 c128 }
    \repeat unfold 4 c64
    \repeat unfold 4 c64
  }
  c32 c
  c32 c
  \break

  c32 c
  c32 c
  \tuplet 3/2 {
    \repeat unfold 4 c64
    \repeat unfold 4 c64
    \tuplet 3/2 { \repeat unfold 12 c128 }
  }
}

```

I'll take a look at the figures on pgs. 7-9 next week


--
- Jason Yip

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