/*************************************************************************\
      "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 128       /* 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.
                            */