/*---------------------------------------------------------------------------*
 *                                   IT++			             *
 *---------------------------------------------------------------------------*
 * Copyright (c) 1995-2001 by Tony Ottosson, Thomas Eriksson, Pål Frenger,   *
 * Tobias Ringström, and Jonas Samuelsson.                                   *
 *                                                                           *
 * Permission to use, copy, modify, and distribute this software and its     *
 * documentation under the terms of the GNU General Public License is hereby *
 * granted. No representations are made about the suitability of this        *
 * software for any purpose. It is provided "as is" without expressed or     *
 * implied warranty. See the GNU General Public License for more details.    *
 *---------------------------------------------------------------------------*/

/*! 
  \file
  \brief Implementation of some specific functions useful in communications.
  \author Tony Ottosson

  1.3

  2003/05/22 08:55:20
*/

#include "comm/commfunc.h"
#include "base/specmat.h"
#include "base/matfunc.h"
#include "base/binary.h"

namespace itpp { 

  bmat graycode(int m)
  {
    if (m == 1) {
      smat temp = "0;1";
      return to_bmat(temp);
    } else {
      bvec temp(1<<(m-1));
      bmat bb	= graycode(m-1);
      bmat out(1<<m, m);
      out.zeros();
      out.set_col(0, concat(zeros_b(1<<(m-1)), ones_b(1<<(m-1))) );
      for (int i=0; i<m-1; i++) {
	temp = bb.get_col(i);
	out.set_col(i+1, concat(temp, reverse(temp)) );
      }
      return out;
    }
  }

  int hamming_distance(const bvec &a, const bvec &b)
  {
    int i, n=0;

    it_assert1(a.size() == b.size(), "hamming_distance()");
    for (i=0; i<a.size(); i++)
      if (a(i) != b(i))
	n++;
    
    return n;
  }

  int weight(const bvec &a)
  {
    int i, n=0;

    for (i=0; i<a.size(); i++)
      if (a(i)==bin(1))
	n++;
    
    return n;
  }

} //namespace itpp