Open todo list

[aescande]

This is an issue to keep track and discuss some necessary or possible todos, a priori minors one (but that could be promoted to full issues if needs be).

• [No impact] Fix typos in comments
• [Low impact] Use Eigen::Ref in the API, instead of const dMatrixType &. This is to avoid the possible creation of a temporary and a copy.
• [Low impact] Remove PROBLEM_DATA from LexLSE, and the associated getter. It is marked as todo REMOVE in the code and is only there for copying the input data of the decomposition before they are overwritten, seemingly for debugging purpose. Alternatively, we could have a debug flag and make the copy only in this case
• [Moderate impact][possible] Replace enums with enum classes, and simplifiy enum field names accordingly.
• [possible] Expose internal memory to avoid the copy of setData. This might be too dangerous for the expected gain.
• [possible] Pass a std::vector or something similar to describe the level sizes. For now this is done by giving a size and a raw pointer. We could deprecate/remove the actual function in favor of the safer version.

[aescande]

Question: is there a practical interest in keeping the aliases dMatrixType, dVectorType or iVectorType, given that they redefine Eigen::MatrixXd, Eigen::VectorXd and Eigen::VectorXi ?

The only reason I could think of would be to keep a column major matrix if Eigen's default has been set to row major by a compiler flag (which is definitely not a common case).