  An explicit C++ library is provided which deals with Zernike Functions over
the unit circle as the main subject. The implementation includes basic means to
evaluate the functions at points inside the unit circle and to convert the
radial and azimuthal parameters to Noll's index and vice versa. Advanced
methods allow to expand products of Zernike Functions into sums of Zernike
Functions, and to convert Zernike Functions to polynomials over the two
Cartesian coordinates and vice versa.
