-// filter.cpp
-double *filter_generate (const FilterType filt_type, double bw, double xmin, double xmax, int n, double param, const DomainType domain, int numint);
-double filter_spatial_response_calc (int filt_type, double x, double bw, double param, int n);
-double filter_spatial_response_analytic (int filt_type, double x, double bw, double param);
-double filter_frequency_response (int filt_type, double u, double bw, double param);
-double sinc (double x, double mult);
-double integral_abscos(double u, double w);
-