Re: [eigen] backporting the vectorized quaternion product to 2.0 ?

[Cyrille Berger <cberger@xxxxxxxxxxx>]

Hi,

Well you could consider to make a 2.1 branch with all the features that are 
backportable (aka that keep API stable) and release that. And declare trunk to 
be future 3.0, and take your time on that.

I will also give my 2 cents on API stability, I think it has always been a bit 
overated (there are very successfull project with totally unstable API), there 
are things that make breakeage very bearable:
1) the changes need to be well documented
2) coinstability of the installation (you do that with the eigen2/3 include), 
3) keeping to have bug fix release of 2.x even after 3.x is available
4) in the case of eigen, it's important that data class of eigen have/get 
stable API/ABI (vectors and matrixes), this would make it possible to have a 
more heterogenous environment (aka use a vector made with an eigen2 library in 
an application used by eigen3) and to be confident in the use of eigen in 
public API of other libraries

Since I haven't the time (unfortunately :( ) to follow eigen development, I 
don't know if the change you are mentioning are affecting your data classes and 
if what I mention in 4) is possible.

-- 
Cyrille Berger