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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library 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 3, or (at your option) any later

// version.

// This library 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 library; see the file COPYING3.  If not see

// <http://www.gnu.org/licenses/>.

// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software

// is hereby granted without fee, provided that the above copyright

// notice appears in all copies, and that both that copyright notice

// and this permission notice appear in supporting documentation. None

// of the above authors, nor IBM Haifa Research Laboratories, make any

// representation about the suitability of this software for any

// purpose. It is provided "as is" without express or implied

// warranty.

/**

 * @file sample_variance.hpp

 * Contains a function for calculating a sample variance

 */

#ifndef PB_DS_SAMPLE_VAR_HPP

#define PB_DS_SAMPLE_VAR_HPP

#include <list>

#include <numeric>

#include <math.h>

#include <iterator>

namespace __gnu_pbds

{

  namespace test

  {

    namespace detail

    {

#define PB_DS_VTYPE typename std::iterator_traits<It>::value_type

      template<typename It>

      PB_DS_VTYPE

      sample_variance(It b, It e, PB_DS_VTYPE sm)

      {

        PB_DS_VTYPE ss = 0;

        size_t num_res = 0;

        while (b != e)

          {

            const PB_DS_VTYPE d =* b - sm;

            ss += d*  d;

            ++num_res;

            ++b;

          }

        if (num_res == 1)

          return 0;

        return ::sqrt(ss / (num_res - 1));

      }

#undef PB_DS_VTYPE

    } // namespace detail

  } // namespace test

} // namespace __gnu_pbds

#endif