| // 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_DISTRIBUTIONS_H_ |
| #define ABSL_RANDOM_INTERNAL_DISTRIBUTIONS_H_ |
| |
| #include <type_traits> |
| |
| #include "absl/meta/type_traits.h" |
| #include "absl/random/internal/distribution_caller.h" |
| #include "absl/random/internal/traits.h" |
| #include "absl/random/internal/uniform_helper.h" |
| |
| namespace absl { |
| namespace random_internal { |
| template <typename D> |
| struct DistributionFormatTraits; |
| |
| // UniformImpl implements the core logic of the Uniform<T> call, which is to |
| // select the correct distribution type, compute the bounds based on the |
| // interval tag, and then generate a value. |
| template <typename NumType, typename TagType, typename URBG> |
| NumType UniformImpl(TagType tag, |
| URBG& urbg, // NOLINT(runtime/references) |
| NumType lo, NumType hi) { |
| static_assert( |
| std::is_arithmetic<NumType>::value, |
| "absl::Uniform<T>() must use an integer or real parameter type."); |
| |
| using distribution_t = |
| UniformDistributionWrapper<absl::decay_t<TagType>, NumType>; |
| using format_t = random_internal::DistributionFormatTraits<distribution_t>; |
| auto a = uniform_lower_bound(tag, lo, hi); |
| auto b = uniform_upper_bound(tag, lo, hi); |
| |
| // TODO(lar): it doesn't make a lot of sense to ask for a random number in an |
| // empty range. Right now we just return a boundary--even though that |
| // boundary is not an acceptable value! Is there something better we can do |
| // here? |
| if (a > b) return a; |
| |
| using gen_t = absl::decay_t<URBG>; |
| return DistributionCaller<gen_t>::template Call<distribution_t, format_t>( |
| &urbg, tag, lo, hi); |
| } |
| |
| // 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>; |
| |
| } // namespace random_internal |
| } // namespace absl |
| |
| #endif // ABSL_RANDOM_INTERNAL_DISTRIBUTIONS_H_ |