This library allows one to build and evaluate arbitrary separable mode-coupling estimators. In practice, its main purpose is to provide a flat-sky lensing estimator code. More generally, one can build estimators and noise functions for convergence, magnification, shear, mixed estimators (for gradient cleaning), split-based lensing, birefringence, patchy tau, etc. and cross-covariances between these.
Instead of having to calculate by hand the separable forms of the above, one
simply provides the mode-coupling and filter expressions, and a
(Mathematica-like) backend factorizes these expressions into FFT-only form
(i.e., no explicit convolutions are required).
Curved sky support does not exist. Adding it is possibly non-trivial, but thoughts and ideas (and PRs!) are highly appreciated. Still, this package can serve as the backend for quick exploration of various kinds of estimators.