Re: Brief details about pkg package manager.

[Andrew Janke]

On 1/27/19 6:28 AM, priyann wrote:
> Thanks a lot Andy.
>
> In the project site.
> https://wiki.octave.org/Summer_of_Code_Project_Ideas#Octave_Package_management
>
> 1.support for multiple version packages
>
> Why should I keep the older version! because we know the newer version comes
> with bugs fixed which were
> occurring in the older version. Isn't newer version = older version + bugs
> fixed!
> then why this facility required?
>
> 2.support for multiple Octave installs
>
> that means there can be multiple octave versions(4.3.0, 4.3.1 etc) on a
> system?
> So, again, what is the profit? 4.3.1 will be better than 4.3.0.
>
> I am not assuming the python 3.x and python 2.x problem.

There are reasons you might want to use multiple versions in both a 
developer and user context.

While ideally, a newer version should be the older version plus new 
features and bug fixes, sometimes new versions also unintentionally 
introduce bugs, too. And sometimes there may be non-back-compatible API 
changes.

And depending on your environment, the newest version of Octave or a 
library might not be readily available to you. Corporate and educational 
environments might be controlled by an IT department that takes a while 
to test and deploy new versions. This would be especially true if Octave 
saw enterprise use. The Windows installation of Octave comes with a 
bunch of packages whose versions are frozen at the time of installer 
creation. Some Linux distros ship with a version of Octave that is 
frozen at the time of the distro's creation. And upgrading takes some 
work; not all users are going to do it right away after every Octave or 
package release.

For Octave developers, it could be useful to have both multiple package 
versions and multiple Octave versions installed side by side. When 
testing a new package version, you might want to switch back and forth 
between the old version and new version to compare their behavior, and 
make sure that your tests are working as expected. And you might want to 
switch between different versions of other packages to ensure 
compatibility with your package.

As for Octave itself, developers might be pulling in versions from "the 
future" to test upcoming releases, or have alternate builds. I currently 
have like eight variants of Octave installed on my machine: 4.4.1, 5.1 
RC1, stable, default, a couple builds with GUI-related patches and 
customizations, a build done with a hacked Qt library, an OpenBLAS 
build, and a 4.2 OpenBLAS build.

Cheers,
Andrew