sqrt.hpp

浮点数基本运算 浮点数的基本运算主要有四则运算、符号处理、大小比较

// Sqrt implementation -*- C++ -*-

// Copyright (C) 2005 Ben T. Bear
//
// This file is part of the BTB's Template<Integer> 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 2, 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 COPYING.  If not, write to
// the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
// MA 02111-1307, USA.

// As a special exception, you may use this file as part of a free
// software library without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to
// produce an executable, this file does not by itself cause the
// resulting executable to be covered by the GNU General Public
// License.  This exception does not however invalidate any other
// reasons why the executable file might be covered by the GNU General
// Public License.

#ifndef __bt2il_sqrt_hpp
#define __bt2il_sqrt_hpp

#include "place.hpp"

namespace btil
{
  template <int n>
  struct sqrt;
  
  template <int n>
  struct __sqrt_two_place
  {
    static const int value = __sqrt_two_place<n-1>::value;
  };
  
#define __sqrt_two_place_def(nn, n)			\
  template <> struct __sqrt_two_place<nn>		\
  { static const int value = n; }
  
  __sqrt_two_place_def (0, 0);
  __sqrt_two_place_def (1, 1);
  __sqrt_two_place_def (4, 2);
  __sqrt_two_place_def (9, 3);
  __sqrt_two_place_def (16, 4);
  __sqrt_two_place_def (25, 5);
  __sqrt_two_place_def (36, 6);
  __sqrt_two_place_def (49, 7);
  __sqrt_two_place_def (64, 8);
  __sqrt_two_place_def (81, 9);


  template <bool finish, int n, int x>
  struct __sqrt_div;
  
  template <int n, int x0>
  struct __sqrt_div<false, n, x0>
  {
  private:
    static const int x = (n / x0 + x0) / 2;
    static const bool finish = (x*x <= n) && ((x+1)*(x+1) > n);
    
  public:
    static const int value = __sqrt_div<finish, n, x>::value;
  };
  
  template <int n, int x>
  struct __sqrt_div<true, n, x>
  {
    static const int value = x;
  };
  
  template <int n>
  struct sqrt
  {
  private:
    static const int p = place<n>::value;
    static const int z = (p % 2 == 1) ? p - 1 : p - 2;
    static const int  h = n / exp10<z>::value;
    
    static const int x0 = (__sqrt_two_place<h>::value
			   * exp10<z / 2>::value);
    
  public:
    static const int value = __sqrt_div<false, n, x0>::value;
  };
  
  template <>
  struct sqrt<0>
  {
    static const int value = 0;
  };
}

#endif