An ongoing project we have is to ensure more popular, well-known C++ libraries are updated to work with C++Builder, and available to you from within GetIt, our package manager. You may have seen a post earlier this year about real-world (non-demo) apps that you can use with C++Builder and CMake, for example, and this is related.
Today, let's look at Eigen.
Eigen is a very famous C++ library for linear algebra. Or, to quote, "Eigen is a C++ template library for linear algebra: matrices, vectors, numerical solvers, and related algorithms."
If you do any kind of moderately complex math in C++, most likely you've come across Eigen, and it regularly pops up as a recommended library.
Eigen is available in GetIt.
When you use RAD Studio, you can mix C++ and Delphi code together. I have a blog post, video, and example source code for doing so, in both directions - adding Delphi to C++, and adding C++ to Delphi! If you want to make use of C++ libraries from within Delphi, check those out, and look into making use of RAD Studio.