Re: [eigen] Eigen2 to Eigen3 Migration Path

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

I have to say that I'm not fan of such a change, and I would feel very
uncomfortable to ask to all users that I encouraged to directly (or
move to) Eigen3 to have to do such a change. Also this implies that
everybody update their Eigen3 copy and their libs at the same time...

I'm also not sure what is the point of mixing Eigen2 and Eigen3 in the
same project since Eigen 2 and 3 objects are not compatible anyway.

The EIGEN2_SUPPORT way seems much more powerful. Let's be specific. If
project A wants to use Eigen3 as well as a lib B which relies on
Eigen2 then there are two cases:
1 - lib B is a pure template lib (or at least the parts which rely on
Eigen2) then EIGEN2_SUPPORT should do the job (we can make it better
if needed).
2 - lib B is a binary library with a public API involving Eigen2
objects. Then there is still the possibility to recompile B with
Eigen3+EIGEN2_SUPPORT.

gael

On Wed, Jan 12, 2011 at 10:24 PM, Hauke Heibel
<hauke.heibel@xxxxxxxxxxxxxx> wrote:
> On Wed, Jan 12, 2011 at 9:48 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
> wrote:
>>
>> Tully's concern is much more serious than that! There is the concern
>> of having Eigen2 and Eigen3 coexist in a single software project,
>> which as discussed is going to stay the case for some time as
>> libraries using Eigen2 port to Eigen3.
>
> Ok, it seems to be all about being able to let Eigen2 and Eigen3 and maybe
> EigenX co-exist. I am fine with that, if that is really what you want to
> support.
> That I am not a fan of this feature is probably a matter of taste. I am
> already thinking of requests such as being able to convert an
> Eigen2::MatrixXf to an Eigen3::MatrixXf.
> - Hauke
>