Comments added

README

@@ -1 +1 @@
-IIR filter using Laplace transform
+Implementation of IIR-filter for given Laplace transform.

dumper.h

@@ -1,3 +1,7 @@
+/*
+    Routines to print polynoms and filter transform functions (used for testing purposes).
+*/
+
 #ifndef DUMPER_H
 #define DUMPER_H
 

filter.c

@@ -3,6 +3,10 @@
 
 #include "filter.h"
 
+#ifdef DEBUG_DUMP
+#include "dumper.h"
+#endif
+
 
 void bilinear_transform_n(const double *s, const int ns, const double t, double *znum, double *zden)
 {
@@ -60,10 +64,10 @@ int bilinear_transform_nd(const double *snum, const int nsnum, const double *sde
     bilinear_transform_n(snum, nsnum, t, znumnum, znumden);
     bilinear_transform_n(sden, nsden, t, zdennum, zdenden);
 
-/*
+#ifdef DEBUG_DUMP
     print_polynom_nd(znumnum, nsnum, znumden, nsnum, 'z', "zn");
     print_polynom_nd(zdennum, nsden, zdenden, nsden, 'z', "zd");
-*/
+#endif // DEBUG_DUMP
 
     clear_polynom(znumden, nsnum);
     clear_polynom(zdenden, nsden);
@@ -216,7 +220,9 @@ IIR_FILTER *laplace_zp_filter(const complex *zlc, const int nzlc,
     expand_zerolist_c(plc, nplc, pkc, den_c);
     copy_polynom_cr(den_c, nden, den);
 
-    //print_polynom_nd(num, nnum, den, nden, 's', "zp nd");
+#ifdef DEBUG_DUMP
+    print_polynom_nd(num, nnum, den, nden, 's', "zp nd");
+#endif // DEBUG_DUMP
 
     return laplace_nd_filter(num, nnum, den, nden, dt, L);
 }

filter.h

@@ -1,30 +1,48 @@
+/*
+    IIR filter-related functions.
+
+*/
+
 #ifndef FILTER_H
 #define FILTER_H
 
 #include "polynom.h"
 
+// IIR-filter
 typedef struct {
+    // Feedforward filter coefficients
     double *b;
     int m;
 
+    // Feedback filter coefficients
     double *a;
     int n;
 
+    // Filter state (input and output signal values history)
     double *x;
     double *y;
 } IIR_FILTER;
 
+// Bilinear transform implementations (https://en.wikipedia.org/wiki/Bilinear_transform)
 void bilinear_transform_n(const double *s, const int ns, const double t, double *znum, double *zden);
 int bilinear_transform_nd(const double *snum, const int nsnum, const double *sden, const int nsden,
     const double t, double *znum, double *zden);
 
+// Create IIR-filter based on given difference equation 
 IIR_FILTER *iir_filter_init(const double *b, const int m, const double *a, const int n);
+
+// Free (destroy) IIR-filter
 void iir_filter_free(IIR_FILTER *iir);
+
+// Get next output value of IIR-filter
 double iir_filter_next(IIR_FILTER *iir, const double x);
 
+// Zero-Denominator Laplace transform IIR-filter
 IIR_FILTER *laplace_nd_filter(const double *num, const int nnum,
     const double *den, const int nden,
     const double dt, const int L);
+
+// Zero-Pole Laplace transform IIR-filter
 IIR_FILTER *laplace_zp_filter(const complex *zlc, const int nzlc,
     const complex *plc, const int nplc,
     const complex zkc, const double dt, const int L);

filter_test.c

@@ -1,3 +1,7 @@
+/*
+    Main module for filter testing.
+*/
+
 #include <stdio.h>
 #include <math.h>
 

polynom.h

@@ -1,3 +1,7 @@
+/*
+    Mini-library of functions to operate polynoms.
+*/
+
 #ifndef POLYNOM_H
 #define POLYNOM_H
 

polynom_test.c

@@ -1,3 +1,7 @@
+/*
+    Main module for polynom operations testing.
+*/
+
 #include <stdio.h>
 
 #include "polynom.h"