C++ default_ops::eval_get_sign方法代码示例

inline typename enable_if_c<!is_trivial_cpp_int<cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1> >::value, unsigned>::type
   eval_lsb(const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& a)
{
   using default_ops::eval_get_sign;
   if(eval_get_sign(a) == 0)
   {
      BOOST_THROW_EXCEPTION(std::range_error("No bits were set in the operand."));
   }
   if(a.sign())
   {
      BOOST_THROW_EXCEPTION(std::range_error("Testing individual bits in negative values is not supported - results are undefined."));
   }

   //
   // Find the index of the least significant limb that is non-zero:
   //
   unsigned index = 0;
   while(!a.limbs()[index] && (index < a.size()))
      ++index;
   //
   // Find the index of the least significant bit within that limb:
   //
   unsigned result = boost::multiprecision::detail::find_lsb(a.limbs()[index]);

   return result + index * cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>::limb_bits;
}

inline typename enable_if_c<is_trivial_cpp_int<cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1> >::value, unsigned>::type
   eval_msb(const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& a)
{
   using default_ops::eval_get_sign;
   if(eval_get_sign(a) == 0)
   {
      BOOST_THROW_EXCEPTION(std::range_error("No bits were set in the operand."));
   }
   if(a.sign())
   {
      BOOST_THROW_EXCEPTION(std::range_error("Testing individual bits in negative values is not supported - results are undefined."));
   }
   return eval_msb_imp(a);
}

void generic_interconvert(To& to, const From& from, const mpl::int_<number_kind_integer>& /*to_type*/, const mpl::int_<number_kind_integer>& /*from_type*/)
{
   using default_ops::eval_get_sign;
   using default_ops::eval_bitwise_and;
   using default_ops::eval_convert_to;
   using default_ops::eval_right_shift;
   using default_ops::eval_left_shift;
   using default_ops::eval_bitwise_or;
   using default_ops::eval_is_zero;
   // smallest unsigned type handled natively by "From" is likely to be it's limb_type:
   typedef typename canonical<unsigned char, From>::type   limb_type;
   // get the corresponding type that we can assign to "To":
   typedef typename canonical<limb_type, To>::type         to_type;
   From t(from);
   bool is_neg = eval_get_sign(t) < 0;
   if(is_neg)
      t.negate();
   // Pick off the first limb:
   limb_type limb;
   limb_type mask = static_cast<limb_type>(~static_cast<limb_type>(0));
   From fl;
   eval_bitwise_and(fl, t, mask);
   eval_convert_to(&limb, fl);
   to = static_cast<to_type>(limb);
   eval_right_shift(t, std::numeric_limits<limb_type>::digits);
   //
   // Then keep picking off more limbs until "t" is zero:
   //
   To l;
   unsigned shift = std::numeric_limits<limb_type>::digits;
   while(!eval_is_zero(t))
   {
      eval_bitwise_and(fl, t, mask);
      eval_convert_to(&limb, fl);
      l = static_cast<to_type>(limb);
      eval_right_shift(t, std::numeric_limits<limb_type>::digits);
      eval_left_shift(l, shift);
      eval_bitwise_or(to, l);
      shift += std::numeric_limits<limb_type>::digits;
   }
   //
   // Finish off by setting the sign:
   //
   if(is_neg)
      to.negate();
}

inline typename enable_if_c<is_trivial_cpp_int<cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1> >::value, unsigned>::type
   eval_msb(const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& a)
{
   using default_ops::eval_get_sign;
   if(eval_get_sign(a) == 0)
   {
      BOOST_THROW_EXCEPTION(std::range_error("No bits were set in the operand."));
   }
   if(a.sign())
   {
      BOOST_THROW_EXCEPTION(std::range_error("Testing individual bits in negative values is not supported - results are undefined."));
   }
   //
   // Find the index of the least significant bit within that limb:
   //
   return boost::multiprecision::detail::find_msb(*a.limbs());
}

inline typename enable_if_c<!is_trivial_cpp_int<cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1> >::value>::type
   eval_gcd(
      cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& result,
      const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& a,
      const cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1>& b)
{
   using default_ops::eval_lsb;
   using default_ops::eval_is_zero;
   using default_ops::eval_get_sign;

   if(a.size() == 1)
   {
      eval_gcd(result, b, *a.limbs());
      return;
   }
   if(b.size() == 1)
   {
      eval_gcd(result, a, *b.limbs());
      return;
   }

   int shift;

   cpp_int_backend<MinBits1, MaxBits1, SignType1, Checked1, Allocator1> u(a), v(b);

   int s = eval_get_sign(u);

   /* GCD(0,x) := x */
   if(s < 0)
   {
      u.negate();
   }
   else if(s == 0)
   {
      result = v;
      return;
   }
   s = eval_get_sign(v);
   if(s < 0)
   {
      v.negate();
   }
   else if(s == 0)
   {
      result = u;
      return;
   }

   /* Let shift := lg K, where K is the greatest power of 2
   dividing both u and v. */

   unsigned us = eval_lsb(u);
   unsigned vs = eval_lsb(v);
   shift = (std::min)(us, vs);
   eval_right_shift(u, us);
   eval_right_shift(v, vs);

   do
   {
      /* Now u and v are both odd, so diff(u, v) is even.
      Let u = min(u, v), v = diff(u, v)/2. */
      s = u.compare(v);
      if(s > 0)
         u.swap(v);
      if(s == 0)
         break;
      if(v.size() <= 2)
      {
         if(v.size() == 1)
            u = integer_gcd_reduce(*v.limbs(), *u.limbs());
         else
         {
            double_limb_type i, j;
            i = v.limbs()[0] | (static_cast<double_limb_type>(v.limbs()[1]) << sizeof(limb_type) * CHAR_BIT);
            j = (u.size() == 1) ? *u.limbs() : u.limbs()[0] | (static_cast<double_limb_type>(u.limbs()[1]) << sizeof(limb_type) * CHAR_BIT);
            u = integer_gcd_reduce(i, j);
         }
         break;
      }
      eval_subtract(v, u);
      vs = eval_lsb(v);
      eval_right_shift(v, vs);
   }
   while(true);

   result = u;
   eval_left_shift(result, shift);
}