Re: Repeat alternative count

[Christopher Heckman]

On Sat, Aug 29, 2020 at 9:00 AM <lilypond-devel-request@gnu.org> wrote:
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 29 Aug 2020 07:00:17 -0700
> From: Aaron Hill <lilypond@hillvisions.com>
> To: lilypond-devel@gnu.org
> Subject: Re: Repeat alternative count
> Message-ID: <7a86cc0e1bc3203a1d685d9e7d431e6f@hillvisions.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> On 2020-08-29 6:37 am, Dan Eble wrote:
> > Is there a use case for specifying the number of times to reuse a
> > repeat alternative in a way that \unfoldRepeats could honor?  Right
> > now, it reuses the first alternative enough times to reach the repeat
> > count.  If so, does anyone want to suggest a syntax?  Here's my entry.
> >
> >     \repeat volta 40 {
> >       …
> >     } \alternative {
> >       { … }
> >       \repeat alternative 3 { … }
> >       { … }
> >     }
> >
> > Good? Bad? Meh?
>
> What would be nice is to have a way to semantically indicate precisely
> when and how many times an alternative is used.
>
> Consider a case when you have a first ending that would be labelled
> "1.3." and a second ending that is labelled "2.4.5.".  Currently, this
> can be done using custom repeat commands but \unfoldRepeats does not
> know how to parse the volta text and produce the right expansion.
>
> Perhaps:
>
> %%%%
> \repeat volta 5 {
>    ...
> }
> \alternative 1,3 {
>    ...
> }
> \alternative 2,4,5 {
>    ...
> }
> %%%%
>
>
> -- Aaron Hill

That would break too many things, since \alternative takes a sequence
of SequentialMusic's as an argument.

How about allowing modifying the syntax of \alternative to include the
possibility of a number, which means to repeat that ending? This would
look like

\alternative {
  { c1 }
  1
  { d1 }
  1
   }

Which would be interpretted as: the 1st, 2nd, and 4th endings are c,
and the 3nd  ending is d.

Obviously, something like \alternative { 1 ... } would be illegal, although
\alternative { 2 { ... } } might be acceptable.

As a bonus, maybe Lilypond could automatically typeset the repeat
numbers based on the \alternative structure? In the example above, we
would have something that looks like

_||__1, 2, 4.___:||__3.___:||__

((A few minutes later)) Those repeat signs might make things a bit
difficult. Perhaps we could include \start-repeat to print a ||: and
\end-repeat to print a :|| ... so that the example above would look
more like

\alternative {
  { c1 \end-repeat }
  1
  { d1 }
  1
   }

to get the following instead:

_||__1, 2, 4.___:||__3.___||__

--- Christopher Heckman