chromium/third_party/abseil-cpp/absl/random/uniform_real_distribution.h

// Copyright 2017 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.
//
// -----------------------------------------------------------------------------
// File: uniform_real_distribution.h
// -----------------------------------------------------------------------------
//
// This header defines a class for representing a uniform floating-point
// distribution over a half-open interval [a,b). You use this distribution in
// combination with an Abseil random bit generator to produce random values
// according to the rules of the distribution.
//
// `absl::uniform_real_distribution` is a drop-in replacement for the C++11
// `std::uniform_real_distribution` [rand.dist.uni.real] but is considerably
// faster than the libstdc++ implementation.
//
// Note: the standard-library version may occasionally return `1.0` when
// default-initialized. See https://bugs.llvm.org//show_bug.cgi?id=18767
// `absl::uniform_real_distribution` does not exhibit this behavior.

#ifndef ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_
#define ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_

#include <cassert>
#include <cmath>
#include <cstdint>
#include <istream>
#include <limits>
#include <type_traits>

#include "absl/meta/type_traits.h"
#include "absl/random/internal/fast_uniform_bits.h"
#include "absl/random/internal/generate_real.h"
#include "absl/random/internal/iostream_state_saver.h"

namespace absl {
ABSL_NAMESPACE_BEGIN

// absl::uniform_real_distribution<T>
//
// This distribution produces random floating-point values uniformly distributed
// over the half-open interval [a, b).
//
// Example:
//
//   absl::BitGen gen;
//
//   // Use the distribution to produce a value between 0.0 (inclusive)
//   // and 1.0 (exclusive).
//   double value = absl::uniform_real_distribution<double>(0, 1)(gen);
//
template <typename RealType = double>
class uniform_real_distribution { … };

// -----------------------------------------------------------------------------
// Implementation details follow
// -----------------------------------------------------------------------------
template <typename RealType>
template <typename URBG>
typename uniform_real_distribution<RealType>::result_type
uniform_real_distribution<RealType>::operator()(
    URBG& gen, const param_type& p) { … }

template <typename CharT, typename Traits, typename RealType>
std::basic_ostream<CharT, Traits>& operator<<(
    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
    const uniform_real_distribution<RealType>& x) { … }

template <typename CharT, typename Traits, typename RealType>
std::basic_istream<CharT, Traits>& operator>>(
    std::basic_istream<CharT, Traits>& is,     // NOLINT(runtime/references)
    uniform_real_distribution<RealType>& x) { … }
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_