Re: Some questions on the interval package

[Oliver Heimlich]

On 15.08.2017 14:58, Joel Dahne wrote:
> Oliver Heimlich writes:
>> On 15.08.2017 12:36, Oliver Heimlich wrote:
>>>>> Given the recent hints on the mailing list regarding bug #46603, I have
>>>>> added support for “format compact” myself.  It has been a little bit
>>>>> complicated to come up with a solution that doesn't use internal
>>>>> functions, doesn't rely on deprecated features, and doesn't break old
>>>>> versions of Octave.
>>>>
>>>> It is indeed a bit complicated. I doesn't work for Octave version 4.2.1,
>>>> which uses __compactformat__ for this. I have attached a patch that
>>>> fixes it for me. But please double check that it works for you as well.
>>>
>>> Thanks for the patch.  I'll make a private utility function from it.
>>
>> Ok, done.  However, during my tests in Octave 3.8.2 I have found out
>> that “get (0, "FormatSpacing")” is broken and always returns "loose".
>>
>> - In Octave < 4.0 there is no way to query that information correctly.
>> - In Octave 4.0.x we have __compactformat__ and get (0, "FormatSpacing")
>> - In Octave 4.2.x we have only __compactformat__
>> - In Octave > 4.3.x we have only [~, spacing] = format ()
> 
> But it at least works for < 4.0? It does not crash?

Currently, it does not crash, but the format for intervals will always
be “loose”.  I know a kludgy workaround, but struggle to use it.

>> Looking through the other BISTs on Octave 3.8.2 (see attachement), I
>> observe:
>>
>> - several warnings because of automatic broadcasting (these warning are
>> disabled in Octave >= 4.0.0 by default)
> 
> Most likely I'm the cause for some of these. I have never tested if for
> < 4.0.

If we keep official support for Octave < 4.0, we have to disable these
warnings in some functions (that is, mainly in the constructors).

>> - errors in the postpad and prepad functions
> 
> Why would that be? It doesn't really use any odd functions.

The old builtin *-pad functions do not allow to increase the number of
dimensions of an array.  The following kind of test tries to do that:

  postpad (infsup (0), 10, 0, 3)

We would need add “if (compare_versions (OCTAVE_VERSION …” around the
test code.

>> - a failing test for disp (see above)
>>
>> Also, I can't use the doctest package on the manual anymore, because of
>> missing SKIP_IF expression support and the latest doctest package has a
>> dependency on Octave 4.0.0.
> 
> It's though when your method for detecting the version does not work on
> some versions...

The old doctest relese did not contain support for SKIP_IF
(…expression…).  The new doctest release requires Octave 4.0.0.  I don't
know how to fix that instead of no longer doctest'ing the manual with
old Octave.  On the other hand, I have no problem with the manual
reflecting the new versions.

>> I guess it's time to drop support for Octave < 4.0.0 in the interval
>> package.
> 
> You are probably right. How much are these used? I believe Ubuntu 14.04
> uses 3.8.1 or something similar. Even if we formally drop support of it
> most things will sort of work at least and we get much less to test
> against.

There is version 3.8.2 in the Google play store (GNURoot Octave), which
I still use on my Android phone.  Also this is the official version in
Debian Jessie, users should upgrade to Debian Stretch (and Octave 4.0.3)
until 2018-06-17 and it is pretty easy to get 4.0.3 from the
jessie-backports repository.  On Windows, I guess most users have
migrated to >= 4.0.0 already, because of the GUI.

My current impression is that the package would still work rather nicely
in 3.8.2 with the following drawbacks:
 - some tests for *-pad functions are broken
 - “format compact” not supported
 - several unnecessary warnings because of broadcasting
 - doctest'ing for the manual is not possible

I guess it will be best if I fix these problems (I can easily test in
3.8.2) and—yes—apply that pesky workaround to make “format compact” work
in 3.8.2.

Oliver