How to integrate a library that uses expression templates?

Question

I would like to use the Eigen matrix library as the linear algebra engine in my program. Eigen uses expression templates to implement lazy evaluation and to simplify loops a

Answer 1

In my opinion, this looks more of a object oriented design problem rather than a library usage problem. Whatever you read from the books are the right recommendations. i.e, do not expose member variables and shield the upper layers from the nuances of the 3rd party layer usage.

What you could look forward is right abstractions of mathematical functions that can be implemented using this library internally. i.e, you could expose a library of your own with high level functions than elementary vector and matrix operations. In this way you can utilize the peculiarities of the interactions among the library objects and at the same time you don't have to expose your member variables to upper layers.

For e.g you could abstract away my higher level APIs like computing the distance from a point to a plane, distance between two planes, computing the new coordinates of a point w.r.t another coordinate system using the transformation matrices etc. To implement these methods internally you can utilize the library objects. You can restrict to not to have any of the library classes used in the API signatures to avoid dependency for the upper layers on this library.

Upper layers of your program should be higher in the level of abstraction and need not bother about the elementary implementation details such as how the calculation of the distance from a point to the plane is implemented etc. Also, they even need not know if this lower layer is implemented using this library or something else. They would just use the interfaces of your library.