Polynomials in arbitrary basis

[Vladislav Malyshkin]

Octave currently has polynomials manipulation functionality
https://octave.org/doc/v4.0.3/Polynomial-Manipulations.html
only in monomials basis: sum c_kx^k
In practice it is often very convenient to have polynomial represented in other polynomials basis: sum c_kQ_k(x)
where the basis  Q_k(x) is orthogonal polynomials of some kind.
There is my implementation of polynomials manipulation functionality (and Gauss-type quadratures calculation) in the basis of Chebyshev, Legendre, Laguerre, Hermite bases.
The code is available under GPL and is java-written (however it will not be much a problem to rewrite it in C/C++).
You can read about code at https://arxiv.org/pdf/1510.05510 see Appendix A & B.
Let me know if you have any interest.
Vladislav
P.S. From the other alternative basis software I know only matlab-written http://www.chebfun.org/ by Alex Townsend, but his project has different goals.