Re: What's the deal with this "programming error"?

[David Kastrup]

"Dmytro O. Redchuk" <address@hidden> writes:

> On Wed 09 Jun 2010, 16:52 David Kastrup wrote:
>
>> Anyway, I should think that this bug description including a list of
>> relevant examples should warrant being recorded by the bug squad.
> i simply can not understand (tm) what's the problem (tm):

The error messages?

> On Thu 03 Jun 2010, 14:34 David Kastrup wrote:
>> When compiling
>> 
>> \new Voice \with {\consists "Ambitus_engraver"}
>> {<<\new Voice { c } s>> { c } }
>> 
>> I get the following two "programming error"s.  What's up?
>> 
>
>> programming error: note column without heads and stem
> note column is _really_ without heads and stem...

At the point of time that the "bug" is reported.  But that time is
premature since respective ambitus data arrives later.

>> continuing, cross fingers
>> /tmp/junk.ly:2:26: programming error: note-column has no direction
>> {<<\new Voice { c } s>> { 
>>                           c } }
> ... well, i can easily believe it _really_ has no direction.

See above.

> Sorry, i _really_ could not catch the idea. So i waited (as usually)
> for some discussion of the topic. And still waiting, be sure .)

The problem is that the ambitus engraver barfs because of a lack of data
that is going to arrive later.

It appears that there are some measures in the engraver that avoid those
messages for some of the simplest cases (see in particular the examples
I gave that _don't_ throw errors), but they don't seem to do the job
properly.

The ambitus engraver tries evaluating something at a time when it does
not work.  Whether or not that is convenient or the only way to do it,
it should not be able to cause errors until the voice actually ends.

And then the error should not be something utterly bewildering, but
clearly pointing to the lack of collected ambitus data.

Does this make the problem clearer?

-- 
David Kastrup