Re: [eigen] Bugs in Mat::Random, reductions

[Benoît Jacob <jacob@xxxxxxxxxxxxxxx>]

I mostly agree with that, but I would like to put one more evolution of this 
solution on the table.

Instead of requiring the user to do
#define EIGEN_USING_ARRAY_MODULE
#define EIGEN_USING_GEOMETRY_MODULE
#include <Eigen/Eigen>

we could do

#include <Eigen/Array>
#include <Eigen/Geometry>
#include <Eigen/Eigen>

In other words, the only difference from the current situation, from the 
user's point of view, is that he must always include Eigen/Eigen last.

Eigen/Array would just do:
1) check that Eigen/Eigen is not already included (#error otherwise)
2) define EIGEN_USING_ARRAY_MODULE

Let me explain why it might still be worth doing that. We brought this 
conversation from the topic of error messages when the user forgets to 
#include a module. But this is a broader issue. The real question is, is it 
potentially useful to let Eigen know globally which modules are #included? 
The issue of error message is just one example of where it is useful to know 
that. There might be more...?

So, I have the feeling that it might be worth asking the user to 
#include<Eigen/Eigen> last.

Opinions?

Benoit



> Since no one complained, I guess nobody is against that solution. On
> the other hand nobody seems to be excited by it, and actually, neither
> do I. I mean, currently we have an intuitive mechanism to include
> modules, but some weird link error messages if someone forgot to
> include the right module.  And the we would change for more intuitive
> error messages but with an unintuitive inclusion mechanism. So
> eventually that's probably not worth it. In both cases we have to
> compensate some unintuitiveness  by big warning in the documentation.
> So let's keep the current state, and improve the doc. isn't it ?
>
> gael.
>
> ---



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