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Diffstat (limited to 'third_party/abseil_cpp/absl/random/internal/uniform_helper.h')
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1 files changed, 210 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/random/internal/uniform_helper.h b/third_party/abseil_cpp/absl/random/internal/uniform_helper.h new file mode 100644 index 0000000000..5b2afecb89 --- /dev/null +++ b/third_party/abseil_cpp/absl/random/internal/uniform_helper.h @@ -0,0 +1,210 @@ +// 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_ |