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ccdbb5941 Export of internal Abseil changes 01f5f81f9 Export of internal Abseil changes 2c92bdc7c Export of internal Abseil changes e7ebf9803 Export of internal Abseil changes 2eba343b5 Export of internal Abseil changes a8b03d90e Export of internal Abseil changes 1d31b5c36 Export of internal Abseil changes da3a87690 Export of internal Abseil changes 8faf20461 Exclude empty directories (#697) 2069dc796 Export of internal Abseil changes 4832bf6bf Added a BUILD file in root to expose license. (#695) af8f994af Export of internal Abseil changes 33caf1097 Export of internal Abseil changes cf1a02e2d Export of internal Abseil changes git-subtree-dir: third_party/abseil_cpp git-subtree-split: ccdbb5941f992fabda7eae3ce72f55efc17c826a
210 lines
7.7 KiB
C++
210 lines
7.7 KiB
C++
// 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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