Re: Allows for easier creation of many Lilypond objects via Scheme. (issue 7009047)

[address@hidden]

On 24 déc. 2012, at 10:36, address@hidden wrote:

On 2012/12/24 07:28:17, mike7 wrote:

On 24 déc. 2012, at 01:10, mailto:address@hidden wrote:

> All of this is absolutely devastatingly horrible code that is not
> reconcilable with sane per-session semantics and tampers with

LilyPond

> internals in a way that has bleed-over effects into future files in

the

> same command line.
>
> In addition, the interfaces into the exposed internals are

absolutely

> horrific and cryptic and don't make any sense as a user interface.
>

I agree that the innards I'm exposing are not coded particularly
well

You don't get the point.  A user interface is not supposed to "expose
innards", it is supposed to provide functionality.  Pulling data
structures and some of the code accessing them into the open is not a
user interface.

I am certainly not saying that this type of task is for every user, but someone comfortable enough to do this should not have to copy and paste from define-*.scm every time.

> This is taking everything that is broken with
> input/regression/scheme-text-spanner.ly, magnifies it to a number of
> other cases, and gives it a bad interface.

I am of the opinion that it is better to have stuff like this that
allows people to do creative and interesting things with LilyPond
than not have it at all.

But those "creative and interesting things" will break frequently on
update.  We already have quite a bit of "why doesn't this stuff I
based on [some version of] scheme-text-spanner.ly not work in my
version of LilyPond?" questions.

It seems like you'd rather not make something accessible rather than making it accessible in a fragile state.  I certainly prefer the latter, as it allows more people to experiment.  For example, David's work on the frame engraver would be a great trial ground for this sort of thing.

This is something that several users have asked for.

But this does not give it to them.  It is just a teaser which we'll
take away again.  It is bad enough if we have teasers in
input/regression.  Teasers don't belong in LilyPond proper.

The whole point seems like by putting it there, we will hold ourselves to the standard of making sure it works should it ever break.  I completely agree that teasers don't belong in LilyPond proper, but I don't see this going away.

> No, no, and no again.  Extensibility in this area would be nice, but
> pulling out LilyPond's innards into the public without a proper

design

> is no substitute for that and totally a step in the wrong direction.

I disagree.  Proper design is important, but people who use LilyPond
want this.

People who use LilyPond want some parts of LilyPond to be extensible.
This is _not_, I repeat _not_ what your patch does.  It just pulls
some internals from LilyPond's non-extensible parts into the open.

And by pulling these out into the open, it allows people to make customizable things.

It is like pulling some wires into the passenger room of a car that
you can short-circuit for stiffening the dampeners and say that
drivers want this.

This doesn't mess up the car for other people.  And yes, drivers do want this!  If there were an ambulance that one had to short-circuit to get me to the hospital, I wouldn't ask the driver not to drive for fear of an improper car design.

It will cause explosions when the gas runs low
when using this, but it is better to have this now than later.

That's exactly my point - it will explode, we'll see how it explodes, and that's exactly what will help us fix it over time.  Unless we can afford a dedicated team of developers that get just-right, perfect interfaces full of bug free code the first time round, this seems like an imperfect but functional way for LilyPond to move forward.  There are very few things in LilyPond that did not evolve because of the using->failing->fixing cycle.

There is some correlation to the desires of drivers, yes.

I don't believe in withholding a capacity from people just because
its design has problems.

Mike, there is no design

Fair enough.

It is not that the "design has problems",
it is that you did not even bother with designing a user interface.

I tried to make it as painless as possible given the current tools.  Again, those who are using it are likely adept enough at LilyPond where they'll be able to do the things in the regtest.

It is just wires sticking out, and it is wires to something that was
never intended to be shorted.

Let the wires stick out and let people experiment!  Us, users, et cetera.  That is, in my opinion, the best way for things to move forward.  What I'm interested in fixing are the bleed-over problems, as of course this patch shouldn't make LilyPond worse, but it should be a first step towards making this functionality what we want it to be.

Yes, let's improve the design, but let's get it out there.  If
anything, that will allow people to poke at it, see where it fails,
and give us the opportunity to make it better.

Mike, that is crap.  If a programmer can't be bothered designing a
user interface, how can "people poking at it" replace that?

People poking around at things is the reason for the majority of great discoveries and advances in the history of mankind.

How can
they better understand what is at issue than the programmer who could
not be bothered creating an actual interface?

I'm not saying they should understand what is at issue - I'm saying they should ignore or use it, be happy when it works, complain that it doesn't, and we move towards making it better.

For one thing,
incrementally patching things up wherever they break is no substitute
for design.

No, not at all, but it is the thing that allows for design to happen.  We will see how these things are used, realize where they fail, patch as we go, and then make a better design once we understand the scope of the problem.  But how can one understand the scope of anything without experimenting?

For another thing, that can only incrementally _mask_
"broken by design" but can never fix it.

We can refine the regtest over time to be
whatever we think it should be.

We have that approach with scheme-text-spanner already, and it is a
continuing embarrassment to tell people "Uh, this will most certainly
not continue working in future versions.  It broke already for you?
Tough."

It is thanks to the existence of this that I have written several pieces that have been necessary to my career as a composer.  If you could voyage into the past and undo the creation of that engraver, that would take away part of my and other's livelihoods.  Sure, you could make the argument that somethings' working and then breaking is more destructive for the livelihoods of people than not having it at all, but I would disagree.  From my experience, it is always better to work with imperfect things and suffer through the pains of breaking and fixing than only letting perfect things pass.

> None of these ad-hoc interfaces can sensibly be guaranteed to
> survive any evolution of LilyPond's operation since they don't
> interface to functionality, but rather to the current internals.

So then let's make the functions and regtest better over time
instead of not releasing it at all.

Mike, you don't even try to understand what I am saying.  The point of
an interface is not to make it "better over time".  An interface is
not supposed to change all the time.

Then what are development versions for?

When we provide an interface, it
needs to be better than sawing off the hood of a car so that people
can reach into it from the driver's seat.

So then help me with this with constructive criticism like that of Marc.

People _can_ already open
the hood and poke around, but there is no guarantee that all the
details will be in the same place with the next iteration.

No, but we'll document the changes and do the best we can to help people adapt.

> If people want to poke LilyPond's internals with a stick, of
> course they can do so with all bad side effects including
> everything breaking possibly on the next update.  But there is no
> point giving them a stick with a handle for that if there is no
> way in which we can guarantee the handle working for longer or
> better than the stick does.

We can guarantee this by fixing it when and if it breaks, like
everything else.

You can't "fix" a thin wrapper, nay merely a coating of internals when
the internals change into something more generally useful.  If this
coating is supposed to be an "interface", you can't change the engine
any more.

I think it's important to have the feature first and make it perfect
later.

But you are not providing a feature.  You are just providing access to
the engine.

How is access to the engine not a feature?

Christmasing, so gotta go, but I will continue to be appreciative of all constructive criticism that can help make this patch realizable for people like me, Jeffrey Treviño who requested it, and David N. who has to copy and paste out of scheme files to make this happen.  All three of us make our living thanks to LilyPond.  I can't speak on their behalves, but I can certainly say that I'd appreciate making this patch as good as possible and getting it into LilyPond so that people can poke at it it rather than not adding it for fear of the issues you discuss above.

Cheers,

MS