Abseil Common Libraries (C++) (grcp 依赖)
https://abseil.io/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
55 lines
2.0 KiB
55 lines
2.0 KiB
// Copyright 2021 The Abseil Authors |
|
// |
|
// Licensed under the Apache License, Version 2.0 (the "License"); |
|
// you may not use this file except in compliance with the License. |
|
// You may obtain a copy of the License at |
|
// |
|
// https://www.apache.org/licenses/LICENSE-2.0 |
|
// |
|
// Unless required by applicable law or agreed to in writing, software |
|
// distributed under the License is distributed on an "AS IS" BASIS, |
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
|
// See the License for the specific language governing permissions and |
|
// limitations under the License. |
|
|
|
#ifndef ABSL_NUMERIC_INTERNAL_REPRESENTATION_H_ |
|
#define ABSL_NUMERIC_INTERNAL_REPRESENTATION_H_ |
|
|
|
#include <limits> |
|
|
|
#include "absl/base/config.h" |
|
|
|
namespace absl { |
|
ABSL_NAMESPACE_BEGIN |
|
namespace numeric_internal { |
|
|
|
// Returns true iff long double is represented as a pair of doubles added |
|
// together. |
|
inline constexpr bool IsDoubleDouble() { |
|
// A double-double value always has exactly twice the precision of a double |
|
// value--one double carries the high digits and one double carries the low |
|
// digits. This property is not shared with any other common floating-point |
|
// representation, so this test won't trigger false positives. For reference, |
|
// this table gives the number of bits of precision of each common |
|
// floating-point representation: |
|
// |
|
// type precision |
|
// IEEE single 24 b |
|
// IEEE double 53 |
|
// x86 long double 64 |
|
// double-double 106 |
|
// IEEE quadruple 113 |
|
// |
|
// Note in particular that a quadruple-precision float has greater precision |
|
// than a double-double float despite taking up the same amount of memory; the |
|
// quad has more of its bits allocated to the mantissa than the double-double |
|
// has. |
|
return std::numeric_limits<long double>::digits == |
|
2 * std::numeric_limits<double>::digits; |
|
} |
|
|
|
} // namespace numeric_internal |
|
ABSL_NAMESPACE_END |
|
} // namespace absl |
|
|
|
#endif // ABSL_NUMERIC_INTERNAL_REPRESENTATION_H_
|
|
|