Re: Issue 4083: Implement \tagGroup command (issue 137920043 by address@hidden)

[dak]

On 2014/09/05 06:59:18, Keith wrote:
> LGTM
> It worked fine on (adapted) examples from the divisi staff issue and
emails.
> Looking at the code, I was confused how it worked without the
\cleansed concept
> of the LSR entries, until I realized un-grouped tags effectively form
their own
> group, so old uses of \keepWithTag ignore tags in the new groups.

[some detailed criticism about documentation and code comments]

It is probably helpful to realize that both documentation and code have
been written with a level of understanding exhibited in
<URL:https://code.google.com/p/lilypond/issues/detail?id=4083#c14> that
I had to backpaddle on in
<URL:https://code.google.com/p/lilypond/issues/detail?id=4083#c20>.

So both the user level documentation as well as the code comments
describe the *implementation* without a proper understanding of the
resulting *semantics*.

And the fundamental semantics are that \keepWithTags works independently
on different tag groups, whether one collects them in one \keepWithTags
command or not.  The implementation of the predicate could be done by
splitting in separate tag groups and then iterating through them,
allowing each of them to vote "no" for keeping music.  The current
implementation is more efficient I think but that's more an accident
than by design.

So it would probably be a good idea to rewrite the
documentation/codecomments from scratch.  It's just sort of drudge work
to start over.

https://codereview.appspot.com/137920043/