ln.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

// ln 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_fn_ln_hpp
#define __bt2il_fn_ln_hpp

#include "fnem.hpp"

namespace btil
{
  namespace fn
  {
    template <typename f>
    struct ln;


    struct __ln2;		// value of ln2


    template <int n>
    struct __ln2_item
    {
      static const double item = __ln2_item<n-1>::item / 9.0;
      static const double ln2_n = __ln2_item<n-1>::ln2_n + item / (2*n+1);
    };

    template <>
    struct __ln2_item<0>
    {
      static const double item = 2.0 / 3.0;
      static const double ln2_n = item;
    };

    struct __ln2
    {
      static const double f_val = __ln2_item<25>::ln2_n;
    };



    template <int n, typename x>
    struct __ln_item
    {
      static const double item = __ln_item<n-1, x>::item * -x::f_val;
      static const double ln_n = __ln_item<n-1, x>::ln_n + item / (n+1);
    };

    template <typename x>
    struct __ln_item<0, x>
    {
      static const double item = x::f_val;
      static const double ln_n = item;
    };

    template <typename f>
    struct ln
    {
      struct m
      {
	static const double f_val = fn2em<f, 2>::m::f_val / 2.0 - 1;
      };
      struct value
      {
	static const double f_val = (__ln_item<60, m>::ln_n
				     + __ln2::f_val * (fn2em<f, 2>::e+1));
      };
    };
  }
}

#endif