C++ default_ops::eval_fpclassify方法代码示例

inline int eval_fpclassify(const logged_adaptor<Backend>& arg)
{
   using default_ops::eval_fpclassify;
   log_prefix_event(arg.value(), "fpclassify");
   int r = eval_fpclassify(arg.value());
   log_postfix_event(arg.value(), r, "fpclassify");
   return r;
}

void generic_interconvert(To& to, const From& from, const mpl::int_<number_kind_floating_point>& /*to_type*/, const mpl::int_<number_kind_floating_point>& /*from_type*/)
{
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable:4127)
#endif
   //
   // The code here only works when the radix of "From" is 2, we could try shifting by other
   // radixes but it would complicate things.... use a string conversion when the radix is other
   // than 2:
   //
   if(std::numeric_limits<number<From> >::radix != 2)
   {
      to = from.str(0, std::ios_base::fmtflags()).c_str();
      return;
   }


   typedef typename canonical<unsigned char, To>::type ui_type;

   using default_ops::eval_fpclassify;
   using default_ops::eval_add;
   using default_ops::eval_subtract;
   using default_ops::eval_convert_to;

   //
   // First classify the input, then handle the special cases:
   //
   int c = eval_fpclassify(from);

   if(c == FP_ZERO)
   {
      to = ui_type(0);
      return;
   }
   else if(c == FP_NAN)
   {
      to = "nan";
      return;
   }
   else if(c == FP_INFINITE)
   {
      to = "inf";
      if(eval_get_sign(from) < 0)
         to.negate();
      return;
   }

   typename From::exponent_type e;
   From f, term;
   to = ui_type(0);

   eval_frexp(f, from, &e);

   static const int shift = std::numeric_limits<boost::intmax_t>::digits - 1;

   while(!eval_is_zero(f))
   {
      // extract int sized bits from f:
      eval_ldexp(f, f, shift);
      eval_floor(term, f);
      e -= shift;
      eval_ldexp(to, to, shift);
      typename boost::multiprecision::detail::canonical<boost::intmax_t, To>::type ll;
      eval_convert_to(&ll, term);
      eval_add(to, ll);
      eval_subtract(f, term);
   }
   typedef typename To::exponent_type to_exponent;
   if((e > (std::numeric_limits<to_exponent>::max)()) || (e < (std::numeric_limits<to_exponent>::min)()))
   {
      to = "inf";
      if(eval_get_sign(from) < 0)
         to.negate();
      return;
   }
   eval_ldexp(to, to, static_cast<to_exponent>(e));
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
}

std::string convert_to_string(Backend b, std::streamsize digits, std::ios_base::fmtflags f)
{
   using default_ops::eval_log10;
   using default_ops::eval_floor;
   using default_ops::eval_pow;
   using default_ops::eval_convert_to;
   using default_ops::eval_multiply;
   using default_ops::eval_divide;
   using default_ops::eval_subtract;
   using default_ops::eval_fpclassify;

   typedef typename mpl::front<typename Backend::unsigned_types>::type ui_type;
   typedef typename Backend::exponent_type exponent_type;

   std::string result;
   bool iszero = false;
   bool isneg = false;
   exponent_type expon = 0;
   std::streamsize org_digits = digits;
   BOOST_ASSERT(digits > 0);

   int fpt = eval_fpclassify(b);

   if(fpt == (int)FP_ZERO)
   {
      result = "0";
      iszero = true;
   }
   else if(fpt == (int)FP_INFINITE)
   {
      if(b.compare(ui_type(0)) < 0)
         return "-inf";
      else
         return ((f & std::ios_base::showpos) == std::ios_base::showpos) ? "+inf" : "inf";
   }
   else if(fpt == (int)FP_NAN)
   {
      return "nan";
   }
   else
   {
      //
      // Start by figuring out the exponent:
      //
      isneg = b.compare(ui_type(0)) < 0;
      if(isneg)
         b.negate();
      Backend t;
      Backend ten;
      ten = ui_type(10);

      eval_log10(t, b);
      eval_floor(t, t);
      eval_convert_to(&expon, t);
      if(-expon > std::numeric_limits<number<Backend> >::max_exponent10 - 3)
      {
         int e = -expon / 2;
         Backend t2;
         eval_pow(t2, ten, e);
         eval_multiply(t, t2, b);
         eval_multiply(t, t2);
         if(expon & 1)
            eval_multiply(t, ten);
      }
      else
      {
         eval_pow(t, ten, -expon);
         eval_multiply(t, b);
      }
      //
      // Make sure we're between [1,10) and adjust if not:
      //
      if(t.compare(ui_type(1)) < 0)
      {
         eval_multiply(t, ui_type(10));
         --expon;
      }
      else if(t.compare(ui_type(10)) >= 0)
      {
         eval_divide(t, ui_type(10));
         ++expon;
      }
      Backend digit;
      ui_type cdigit;
      //
      // Adjust the number of digits required based on formatting options:
      //
      if(((f & std::ios_base::fixed) == std::ios_base::fixed) && (expon != -1))
         digits += expon + 1;
      if((f & std::ios_base::scientific) == std::ios_base::scientific)
         ++digits;
      //
      // Extract the digits one at a time:
      //
      for(unsigned i = 0; i < digits; ++i)
      {
         eval_floor(digit, t);
         eval_convert_to(&cdigit, digit);
         result += static_cast<char>('0' + cdigit);
         eval_subtract(t, digit);
//.........这里部分代码省略.........

inline int eval_fpclassify(const debug_adaptor<Backend>& arg)
{
   using default_ops::eval_fpclassify;
   return eval_fpclassify(arg.value());
}