Truncating an oversampled polynomial representation back to the original
representation.
Note, that the oversampled array, which is given as an input here is
is always a Q-Polynomial representation, while the target truncated state
might also be a P-Polynomial.
Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.