fnconst.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

// Pi implementation -*- C++ -*-
//
// Copyright (C) 2005 Ben T. Bear
//
// This file is published under GNU GPL 2.0. See more in "copy.hpp".

// #include "copy.hpp"

#ifndef __bt2il_fn_const_hpp
#define __bt2il_fn_const_hpp

#include "fn.hpp"
#include "fnmath.hpp"
#include "fnexp.hpp"

namespace btil
{
  namespace fn
  {
    struct pi;

    struct e;

    struct one;

    struct two;

    struct three;

    struct ten;

    struct sqrt_two;

    struct sqrt_three;

    struct ln_two;
    
    struct ln_ten;
    
    struct lg_e;




    struct one
    {
      static const double f_val = 1.0;
    };

    struct two
    {
      static const double f_val = 2.0;
    };

    struct three
    {
      static const double f_val = 3.0;
    };


    struct ten
    {
      static const double f_val = 10.0;
    };

    struct ln_ten
    {
      static const double f_val = __ln_ten::f_val;
    };

    struct  lg_e
    {
      static const double f_val = __lg_e::f_val;
    };

    struct sqrt_two
    {
      static const double f_val = sqrt<two>::value::f_val;
    };

    struct sqrt_three
    {
      static const double f_val = sqrt<three>::value::f_val;
    };


    struct ln_two
    {
      static const double f_val = __ln2::f_val;
    };


    template <int n>
    struct __pi_item;
    
    template <>
    struct __pi_item<0>
    {
      static const double item = 0.0;

      static const double pi_n = 2.0;
    };


    template <int n>
    struct __pi_item
    {
      static const double a = 2.0 + __pi_item<n-1>::item;
      static const double x0 = 2.0;
      static const double x1 = (a / x0 + x0) / 2.0;
      static const double x2 = (a / x1 + x1) / 2.0;
      static const double x3 = (a / x2 + x2) / 2.0;
      static const double x4 = (a / x3 + x3) / 2.0;
      static const double x5 = (a / x4 + x4) / 2.0;
      static const double x6 = (a / x5 + x5) / 2.0;
      static const double x7 = (a / x6 + x6) / 2.0;
      static const double x8 = (a / x7 + x7) / 2.0;
      static const double x = x8;

      static const double item = x;

      static const double pi_n = __pi_item<n-1>::pi_n * 2.0 / x;
    };


    struct pi
    {
      static const double f_val = __pi_item<35>::pi_n;
    };


    struct e
    {
      static const double f_val = __e::f_val;
    };

  }
}

#endif