[eigen] Strange issue with Array of Array3f

[Wenzel Jakob <wenzel@xxxxxxxxxxxxxxxxxxxx>]

Hi everyone,

I wanted to point your attention to a strange issue my colleague Wojciech Jarosz has encountered when working with Arrays of RGB color data (encoded using as Array3f).

Please see the StackOverflow report for details: http://stackoverflow.com/questions/32277887/using-eigen-array-of-arrays-for-rgb-images

This is a minimal snippet of code illustrating the issue.

#include <Eigen/Core>

using namespace Eigen;

int main(void)

{

    typedef Array<Array3f, Dynamic, Dynamic> MyArray;

    MyArray m(2,2);

    // all of the following should have the same mathematical effect

    Array3f v = -Array3f(5.0f);             // this compiles

    MyArray a = m + v;                      // this compiles

    MyArray b = m + Array3f(-5.0f);         // this compiles

    MyArray c = m + (-Array3f(5.0f));       // this doesn't compile

    MyArray d = m - Array3f(5.0f);          // this doesn't compile

}

Any thoughts or suggestions would be greatly appreciated.

Thank you,

Wenzel