double_lagrange.h

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/*
 * SPUC - Signal processing using C++ - A DSP library
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
//
#ifndef DLAGRANGE
#define DLAGRANGE
#include <complex.h>
namespace SPUC {
class double_lagrange
{
      public: 
                long num_taps;
        double* coeff;
      protected:
        double* z; 
        double output;
      
      public: 
      // Get current output
      double out() { return(output); }
      // Clock in new sample & compute current output
      //double clock(double in) { return(update(in)); }    
      double check(long i) { return(z[i]); }
        
          double_lagrange(void) { };
          double_lagrange(long n) : num_taps(n) {
                int i;
                coeff = new double[n];
                z = new double[n];
                for (i=0;i<n;i++) z[i] = coeff[i] = 0;  
        } 
          void set_size(long n) {
                int i;
                num_taps = n;
                coeff = new double[n];
                z = new double[n];
                for (i=0;i<n;i++) z[i] = coeff[i] = 0;  
        } 
        // Update
        double update(double in, double offset) {
                int i;                                                       
                // Update history of inputs
                for (i=num_taps;i>0;i--) z[i] = z[i-1];  
                // Add new input
                z[0] = in;   
                // Calculate coefficients
                for (k=0;k<n;k++) {
                        coeff[k] = 1;
                        for (i=0;i<n;i++) {
                                if (k!=i) coeff[i] *= (offset-i)/(k-i);
                        }
                // Perform FIR
                for (output=0,i=0;i<num_taps;i++) output += coeff[i]*z[i];
                return(output);
        }
};
} // namespace SPUC 
#endif      

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