/*************************************************************************\
      "remez.h": include file for programs to link with "remez.o"
 (for design of FIR linear phase filters by the Remez Exchange algorithm)
\*************************************************************************/

#define NFMAX 256           /* max. filter length */
extern float h[ NFMAX ];    /* impulse response of the computed filter */
extern int remez_talk;      /* terminal output while calculating? */
extern int remez_dot;       /* simple output: one dot for each iteration */

int makefilter(int length); /* call this to do the job */
#define REMEZ_OK        0   /* possible return values: */
#define REMEZ_UNSURE    1   /* <- indicate convergence problems */
#define REMEZ_FAIL      2   /* <- */
#define FILTER_TOO_LONG 3   /* length > NFMAX? */
float extreme(float freq);  /* Returns an extremal value of the frequency
                             * response, to be precise: the one that is
                             * nearest to the specified frequency
                             * (0<=freq<=0.5). Example: for a low pass
                             * filter you could call extreme(0) and
                             * extreme(0.5). Let the return values be
                             * 0.985 and -0.0015, then you can tell that
                             * the pass band ripple is +/-1.5 %, the stop
                             * band attenuation -56 dB.
                             */

/* These two functions must be implemented in the calling program: */
float desire(float freq);   /* Magnitude of response,
                             * where freq is the normalized frequency.
                             * Prepare for values 0<=freq<=0.5.
                             */
float weight(float freq);   /* Which parts of the frequency response are
                             * more importantant?
                             * Stop bands usually are, and make sure that
                             * there are always transition bands (with a
                             * weight of 0, i. e. undefined response)
                             * between pass bands and stop bands. The wider
                             * the transition bands, the less ripples in
                             * the other bands can be achieved.
                             */