=== FILES TO MODIFY (in `Macaulay2/e/`)
* `eigen.{h,c}pp` contains service functions for using Eigen library
* `mat-linalg.hpp`

=== IMPLEMENTED
* SVD
  * divide-and-conquer --- either update docs (it is not present in eigen) or eliminate (???)
* eigenvalues

=== NOT IMPLEMENTED YET
* eigenvectors 
* documentation / examples

=== Eigen "manual"
https://eigen.tuxfamily.org/dox/classEigen_1_1ComplexEigenSolver.html#a3aa5e27800349990778da8fa532c1270

