| // Copyright 2019 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_RANDOM_INTERNAL_UNIFORM_HELPER_H_ |
| #define ABSL_RANDOM_INTERNAL_UNIFORM_HELPER_H_ |
| |
| #include <cmath> |
| #include <limits> |
| #include <type_traits> |
| |
| #include "absl/base/config.h" |
| #include "absl/meta/type_traits.h" |
| #include "absl/random/internal/traits.h" |
| |
| namespace absl { |
| ABSL_NAMESPACE_BEGIN |
| |
| template <typename IntType> |
| class uniform_int_distribution; |
| |
| template <typename RealType> |
| class uniform_real_distribution; |
| |
| // Interval tag types which specify whether the interval is open or closed |
| // on either boundary. |
| |
| namespace random_internal { |
| template <typename T> |
| struct TagTypeCompare {}; |
| |
| template <typename T> |
| constexpr bool operator==(TagTypeCompare<T>, TagTypeCompare<T>) { |
| // Tags are mono-states. They always compare equal. |
| return true; |
| } |
| template <typename T> |
| constexpr bool operator!=(TagTypeCompare<T>, TagTypeCompare<T>) { |
| return false; |
| } |
| |
| } // namespace random_internal |
| |
| struct IntervalClosedClosedTag |
| : public random_internal::TagTypeCompare<IntervalClosedClosedTag> {}; |
| struct IntervalClosedOpenTag |
| : public random_internal::TagTypeCompare<IntervalClosedOpenTag> {}; |
| struct IntervalOpenClosedTag |
| : public random_internal::TagTypeCompare<IntervalOpenClosedTag> {}; |
| struct IntervalOpenOpenTag |
| : public random_internal::TagTypeCompare<IntervalOpenOpenTag> {}; |
| |
| namespace random_internal { |
| |
| // In the absence of an explicitly provided return-type, the template |
| // "uniform_inferred_return_t<A, B>" is used to derive a suitable type, based on |
| // the data-types of the endpoint-arguments {A lo, B hi}. |
| // |
| // Given endpoints {A lo, B hi}, one of {A, B} will be chosen as the |
| // return-type, if one type can be implicitly converted into the other, in a |
| // lossless way. The template "is_widening_convertible" implements the |
| // compile-time logic for deciding if such a conversion is possible. |
| // |
| // If no such conversion between {A, B} exists, then the overload for |
| // absl::Uniform() will be discarded, and the call will be ill-formed. |
| // Return-type for absl::Uniform() when the return-type is inferred. |
| template <typename A, typename B> |
| using uniform_inferred_return_t = |
| absl::enable_if_t<absl::disjunction<is_widening_convertible<A, B>, |
| is_widening_convertible<B, A>>::value, |
| typename std::conditional< |
| is_widening_convertible<A, B>::value, B, A>::type>; |
| |
| // The functions |
| // uniform_lower_bound(tag, a, b) |
| // and |
| // uniform_upper_bound(tag, a, b) |
| // are used as implementation-details for absl::Uniform(). |
| // |
| // Conceptually, |
| // [a, b] == [uniform_lower_bound(IntervalClosedClosed, a, b), |
| // uniform_upper_bound(IntervalClosedClosed, a, b)] |
| // (a, b) == [uniform_lower_bound(IntervalOpenOpen, a, b), |
| // uniform_upper_bound(IntervalOpenOpen, a, b)] |
| // [a, b) == [uniform_lower_bound(IntervalClosedOpen, a, b), |
| // uniform_upper_bound(IntervalClosedOpen, a, b)] |
| // (a, b] == [uniform_lower_bound(IntervalOpenClosed, a, b), |
| // uniform_upper_bound(IntervalOpenClosed, a, b)] |
| // |
| template <typename IntType, typename Tag> |
| typename absl::enable_if_t< |
| absl::conjunction< |
| std::is_integral<IntType>, |
| absl::disjunction<std::is_same<Tag, IntervalOpenClosedTag>, |
| std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
| IntType> |
| uniform_lower_bound(Tag, IntType a, IntType) { |
| return a + 1; |
| } |
| |
| template <typename FloatType, typename Tag> |
| typename absl::enable_if_t< |
| absl::conjunction< |
| std::is_floating_point<FloatType>, |
| absl::disjunction<std::is_same<Tag, IntervalOpenClosedTag>, |
| std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
| FloatType> |
| uniform_lower_bound(Tag, FloatType a, FloatType b) { |
| return std::nextafter(a, b); |
| } |
| |
| template <typename NumType, typename Tag> |
| typename absl::enable_if_t< |
| absl::disjunction<std::is_same<Tag, IntervalClosedClosedTag>, |
| std::is_same<Tag, IntervalClosedOpenTag>>::value, |
| NumType> |
| uniform_lower_bound(Tag, NumType a, NumType) { |
| return a; |
| } |
| |
| template <typename IntType, typename Tag> |
| typename absl::enable_if_t< |
| absl::conjunction< |
| std::is_integral<IntType>, |
| absl::disjunction<std::is_same<Tag, IntervalClosedOpenTag>, |
| std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
| IntType> |
| uniform_upper_bound(Tag, IntType, IntType b) { |
| return b - 1; |
| } |
| |
| template <typename FloatType, typename Tag> |
| typename absl::enable_if_t< |
| absl::conjunction< |
| std::is_floating_point<FloatType>, |
| absl::disjunction<std::is_same<Tag, IntervalClosedOpenTag>, |
| std::is_same<Tag, IntervalOpenOpenTag>>>::value, |
| FloatType> |
| uniform_upper_bound(Tag, FloatType, FloatType b) { |
| return b; |
| } |
| |
| template <typename IntType, typename Tag> |
| typename absl::enable_if_t< |
| absl::conjunction< |
| std::is_integral<IntType>, |
| absl::disjunction<std::is_same<Tag, IntervalClosedClosedTag>, |
| std::is_same<Tag, IntervalOpenClosedTag>>>::value, |
| IntType> |
| uniform_upper_bound(Tag, IntType, IntType b) { |
| return b; |
| } |
| |
| template <typename FloatType, typename Tag> |
| typename absl::enable_if_t< |
| absl::conjunction< |
| std::is_floating_point<FloatType>, |
| absl::disjunction<std::is_same<Tag, IntervalClosedClosedTag>, |
| std::is_same<Tag, IntervalOpenClosedTag>>>::value, |
| FloatType> |
| uniform_upper_bound(Tag, FloatType, FloatType b) { |
| return std::nextafter(b, (std::numeric_limits<FloatType>::max)()); |
| } |
| |
| // UniformDistribution selects either absl::uniform_int_distribution |
| // or absl::uniform_real_distribution depending on the NumType parameter. |
| template <typename NumType> |
| using UniformDistribution = |
| typename std::conditional<std::is_integral<NumType>::value, |
| absl::uniform_int_distribution<NumType>, |
| absl::uniform_real_distribution<NumType>>::type; |
| |
| // UniformDistributionWrapper is used as the underlying distribution type |
| // by the absl::Uniform template function. It selects the proper Abseil |
| // uniform distribution and provides constructor overloads that match the |
| // expected parameter order as well as adjusting distribtuion bounds based |
| // on the tag. |
| template <typename NumType> |
| struct UniformDistributionWrapper : public UniformDistribution<NumType> { |
| template <typename TagType> |
| explicit UniformDistributionWrapper(TagType, NumType lo, NumType hi) |
| : UniformDistribution<NumType>( |
| uniform_lower_bound<NumType>(TagType{}, lo, hi), |
| uniform_upper_bound<NumType>(TagType{}, lo, hi)) {} |
| |
| explicit UniformDistributionWrapper(NumType lo, NumType hi) |
| : UniformDistribution<NumType>( |
| uniform_lower_bound<NumType>(IntervalClosedOpenTag(), lo, hi), |
| uniform_upper_bound<NumType>(IntervalClosedOpenTag(), lo, hi)) {} |
| |
| explicit UniformDistributionWrapper() |
| : UniformDistribution<NumType>(std::numeric_limits<NumType>::lowest(), |
| (std::numeric_limits<NumType>::max)()) {} |
| }; |
| |
| } // namespace random_internal |
| ABSL_NAMESPACE_END |
| } // namespace absl |
| |
| #endif // ABSL_RANDOM_INTERNAL_UNIFORM_HELPER_H_ |