Abseil Common Libraries (C++) (grcp 依赖)
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210 lines
7.7 KiB
210 lines
7.7 KiB
// Copyright 2019 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// |
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#ifndef ABSL_RANDOM_INTERNAL_UNIFORM_HELPER_H_ |
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#define ABSL_RANDOM_INTERNAL_UNIFORM_HELPER_H_ |
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#include <cmath> |
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#include <limits> |
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#include <type_traits> |
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#include "absl/base/config.h" |
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#include "absl/meta/type_traits.h" |
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#include "absl/random/internal/traits.h" |
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namespace absl { |
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ABSL_NAMESPACE_BEGIN |
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template <typename IntType> |
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class uniform_int_distribution; |
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template <typename RealType> |
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class uniform_real_distribution; |
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// Interval tag types which specify whether the interval is open or closed |
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// on either boundary. |
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namespace random_internal { |
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template <typename T> |
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struct TagTypeCompare {}; |
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template <typename T> |
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constexpr bool operator==(TagTypeCompare<T>, TagTypeCompare<T>) { |
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// Tags are mono-states. They always compare equal. |
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return true; |
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} |
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template <typename T> |
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constexpr bool operator!=(TagTypeCompare<T>, TagTypeCompare<T>) { |
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return false; |
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} |
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} // namespace random_internal |
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struct IntervalClosedClosedTag |
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: public random_internal::TagTypeCompare<IntervalClosedClosedTag> {}; |
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struct IntervalClosedOpenTag |
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: public random_internal::TagTypeCompare<IntervalClosedOpenTag> {}; |
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struct IntervalOpenClosedTag |
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: public random_internal::TagTypeCompare<IntervalOpenClosedTag> {}; |
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struct IntervalOpenOpenTag |
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: public random_internal::TagTypeCompare<IntervalOpenOpenTag> {}; |
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namespace random_internal { |
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// In the absence of an explicitly provided return-type, the template |
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// "uniform_inferred_return_t<A, B>" is used to derive a suitable type, based on |
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// the data-types of the endpoint-arguments {A lo, B hi}. |
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// |
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// Given endpoints {A lo, B hi}, one of {A, B} will be chosen as the |
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// return-type, if one type can be implicitly converted into the other, in a |
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// lossless way. The template "is_widening_convertible" implements the |
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// compile-time logic for deciding if such a conversion is possible. |
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// |
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// If no such conversion between {A, B} exists, then the overload for |
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// absl::Uniform() will be discarded, and the call will be ill-formed. |
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// Return-type for absl::Uniform() when the return-type is inferred. |
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template <typename A, typename B> |
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using uniform_inferred_return_t = |
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absl::enable_if_t<absl::disjunction<is_widening_convertible<A, B>, |
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is_widening_convertible<B, A>>::value, |
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typename std::conditional< |
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is_widening_convertible<A, B>::value, B, A>::type>; |
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// The functions |
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// uniform_lower_bound(tag, a, b) |
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// and |
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// uniform_upper_bound(tag, a, b) |
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// are used as implementation-details for absl::Uniform(). |
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// |
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// Conceptually, |
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// [a, b] == [uniform_lower_bound(IntervalClosedClosed, a, b), |
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// uniform_upper_bound(IntervalClosedClosed, a, b)] |
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// (a, b) == [uniform_lower_bound(IntervalOpenOpen, a, b), |
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// uniform_upper_bound(IntervalOpenOpen, a, b)] |
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// [a, b) == [uniform_lower_bound(IntervalClosedOpen, a, b), |
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// uniform_upper_bound(IntervalClosedOpen, a, b)] |
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// (a, b] == [uniform_lower_bound(IntervalOpenClosed, a, b), |
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// uniform_upper_bound(IntervalOpenClosed, a, b)] |
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// |
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template <typename IntType, typename Tag> |
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typename absl::enable_if_t< |
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absl::conjunction< |
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std::is_integral<IntType>, |
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absl::disjunction<std::is_same<Tag, IntervalOpenClosedTag>, |
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std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
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IntType> |
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uniform_lower_bound(Tag, IntType a, IntType) { |
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return a + 1; |
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} |
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template <typename FloatType, typename Tag> |
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typename absl::enable_if_t< |
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absl::conjunction< |
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std::is_floating_point<FloatType>, |
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absl::disjunction<std::is_same<Tag, IntervalOpenClosedTag>, |
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std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
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FloatType> |
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uniform_lower_bound(Tag, FloatType a, FloatType b) { |
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return std::nextafter(a, b); |
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} |
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template <typename NumType, typename Tag> |
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typename absl::enable_if_t< |
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absl::disjunction<std::is_same<Tag, IntervalClosedClosedTag>, |
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std::is_same<Tag, IntervalClosedOpenTag>>::value, |
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NumType> |
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uniform_lower_bound(Tag, NumType a, NumType) { |
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return a; |
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} |
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template <typename IntType, typename Tag> |
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typename absl::enable_if_t< |
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absl::conjunction< |
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std::is_integral<IntType>, |
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absl::disjunction<std::is_same<Tag, IntervalClosedOpenTag>, |
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std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
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IntType> |
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uniform_upper_bound(Tag, IntType, IntType b) { |
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return b - 1; |
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} |
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template <typename FloatType, typename Tag> |
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typename absl::enable_if_t< |
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absl::conjunction< |
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std::is_floating_point<FloatType>, |
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absl::disjunction<std::is_same<Tag, IntervalClosedOpenTag>, |
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std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
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FloatType> |
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uniform_upper_bound(Tag, FloatType, FloatType b) { |
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return b; |
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} |
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template <typename IntType, typename Tag> |
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typename absl::enable_if_t< |
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absl::conjunction< |
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std::is_integral<IntType>, |
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absl::disjunction<std::is_same<Tag, IntervalClosedClosedTag>, |
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std::is_same<Tag, IntervalOpenClosedTag>>>::value, |
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IntType> |
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uniform_upper_bound(Tag, IntType, IntType b) { |
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return b; |
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} |
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template <typename FloatType, typename Tag> |
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typename absl::enable_if_t< |
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absl::conjunction< |
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std::is_floating_point<FloatType>, |
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absl::disjunction<std::is_same<Tag, IntervalClosedClosedTag>, |
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std::is_same<Tag, IntervalOpenClosedTag>>>::value, |
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FloatType> |
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uniform_upper_bound(Tag, FloatType, FloatType b) { |
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return std::nextafter(b, (std::numeric_limits<FloatType>::max)()); |
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} |
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// UniformDistribution selects either absl::uniform_int_distribution |
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// or absl::uniform_real_distribution depending on the NumType parameter. |
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template <typename NumType> |
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using UniformDistribution = |
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typename std::conditional<std::is_integral<NumType>::value, |
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absl::uniform_int_distribution<NumType>, |
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absl::uniform_real_distribution<NumType>>::type; |
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// UniformDistributionWrapper is used as the underlying distribution type |
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// by the absl::Uniform template function. It selects the proper Abseil |
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// uniform distribution and provides constructor overloads that match the |
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// expected parameter order as well as adjusting distribtuion bounds based |
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// on the tag. |
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template <typename NumType> |
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struct UniformDistributionWrapper : public UniformDistribution<NumType> { |
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template <typename TagType> |
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explicit UniformDistributionWrapper(TagType, NumType lo, NumType hi) |
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: UniformDistribution<NumType>( |
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uniform_lower_bound<NumType>(TagType{}, lo, hi), |
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uniform_upper_bound<NumType>(TagType{}, lo, hi)) {} |
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explicit UniformDistributionWrapper(NumType lo, NumType hi) |
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: UniformDistribution<NumType>( |
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uniform_lower_bound<NumType>(IntervalClosedOpenTag(), lo, hi), |
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uniform_upper_bound<NumType>(IntervalClosedOpenTag(), lo, hi)) {} |
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explicit UniformDistributionWrapper() |
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: UniformDistribution<NumType>(std::numeric_limits<NumType>::lowest(), |
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(std::numeric_limits<NumType>::max)()) {} |
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}; |
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} // namespace random_internal |
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ABSL_NAMESPACE_END |
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} // namespace absl |
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#endif // ABSL_RANDOM_INTERNAL_UNIFORM_HELPER_H_
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