Re: [eigen] On a flexible API for submatrices, slicing, indexing, masking, etc.

[Peter <list@xxxxxxxxxxxxxxxxx>]

Hi Gael,


Am 22.12.2016 um 11:49 schrieb Gael Guennebaud:

> this is probably one of the most awaited feature that is still shamefully missing in Eigen. So let's have it for 3.4!
indeed, that's a missing feature.


> To help discussion, I've prepare this wiki page that contains a compilable c++ example demonstrating some ideas:
> http://eigen.tuxfamily.org/index.php?title=Working_notes_-_Indexing%2B%2B

Thanks for the references, quite instructive.
The notation using the curly brackets looks pretty nice.
I'm a little bit afraid of getting confused with initialization,
but we have the same in octave and it works.
It would still be great if one could access rows or columns with an arbitrary
list/array, e.g. to sort eigen vectors without moving them in memory.
Currently I use external lists for that.

> Speaking about "ambiguous" API, I hate the current MatrixXd::Constant(...) and VectorXd::LinSpaced(...) function: I never managed to remember the parameter orders, do the sizes come first? or last? I guess this is because the two
> answers make sense: one is consistent when moving from Constant to Ones, and the other when moving from Matrix to Vector or fixed-size object. This is thus a high source of hard to track bugs. I'd really like to avoid this caveat.
well , I was pleased to find it at all, but it's true, I always have to look in the manual
before using it.


Best regards,
Peter