Re: stepping down as project manager

[David Kastrup]

Reinhold Kainhofer <address@hidden> writes:

> On 2012-10-13 23:44, David Kastrup wrote:
>> \once creates a one-time-step temporary change, \temporary an
>> unterminated temporary change which can be terminated element-wise with
>> \revert
>
> +1
> That's a consistent naming scheme, and \temporary is a perfect match
> with \once, so I'm all for that name. \once changes the value for one
> step, \temporary until it is explicitly \revert'ed (und unfortunately
> \override alone permanantly overwrites rather than overrides).

It is so that \override ... \override ... \override ... \revert gets
back to the initial state (though with a net pop, so you better start
out on an empty stack).  Those overrides can come in packages, like

\voiceOne ... \voiceTwo ... \voiceOne ... \oneVoice

and many of those packages are designed to be used in a non-stack-like
manner, presumably because some of them contain a mixture of overrides
and reverts and/or Han-Wen had given up on teaching people about popping
everything they pushed.

If you want the above to return to its original state even in case of a
non-empty stack, it turns out that writing \temporary before the first
\voiceOne will do the trick, but that requires the knowledge that those
commands are organized as a matched set.  The safe/blackbox way to do it
would be to \temporary every \voiceXXX command, and afterwards \undo it,
and that presumably was the original design.

It apparently (as I said, this was done in an only loosely related large
2005 commit without comments, without mention in the log files and
commit messages and apparently without preceding discussion) was changed
after it turned out that users were not coping well with stacks.

The current semantics are basically non-stack, but the stack can be
reanimated temporarily from the Scheme layer.

This reanimation makes sense from the user layer in some cases as well,
particularly when we are talking about "programming" in LilyPond
(writing reusable parts), something which was considered more of an
oddity/curiosity in 2005 than it is now.

So based on the assumption that Han-Wen's stealthy change was due to a
stack having shown itself to be too complex for "normal (TM)" users, it
makes sense to structure the documentation for \temporary/undo in
relation to the basic \override/revert such that the user is comfortable
_not_ being familiar with them while at the same time having access to
the advanced information should he ever need it.  It is not a must-learn
item, but a good-to-know-occasionally one.

-- 
David Kastrup