tvl-depot/absl/random/internal/distributions.h
Abseil Team 97c1664b4b Export of internal Abseil changes
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167cd2647144583746311129b0cc98a89a9897e1 by Andy Soffer <asoffer@google.com>:

Internal Changes

PiperOrigin-RevId: 268000987

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ab44fea7dfdaf763c69609a08ddfac22480ce520 by Derek Mauro <dmauro@google.com>:

Fix flags Cmake tests on Windows

PiperOrigin-RevId: 267859442

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d7ec9f7611370b01bc9a5aed7e18460df2a15429 by Abseil Team <absl-team@google.com>:

Fix undefined behavior in symbolize_elf.inc

PiperOrigin-RevId: 267684904

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e7c5f8e472a91ed99bdf4876942f2bda5751aa6c by Abseil Team <absl-team@google.com>:

Turn off ABSL_HAS_ALARM on Fuchsia.

PiperOrigin-RevId: 267666090

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b7d25d5c71a49e697a8bf6440ed30f2e3f036420 by Chris Kennelly <ckennelly@google.com>:

Mark once initialization function as no inline.

We expect this code to run infrequently.

PiperOrigin-RevId: 267649713

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dc2a5e5f1e39a03fff837d34a319033fde55d9ba by Derek Mauro <dmauro@google.com>:

Fix the MSVC CMake random build

PiperOrigin-RevId: 267624074

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ba2751b67fa17d1b6c53e5ba79f81a5371e4a03a by Abseil Team <absl-team@google.com>:

Move "internal/flag.*" files to the "internal" build target.

PiperOrigin-RevId: 267588996

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05b985a33eec4f8acff1809ad9218a1e22220f34 by Abseil Team <absl-team@google.com>:

Move "internal/flag.*" files to the "internal" build target.

PiperOrigin-RevId: 267580412
GitOrigin-RevId: 167cd2647144583746311129b0cc98a89a9897e1
Change-Id: Ibd334f46a5671c7c1d3fcf5354029e2fbb7ba91f
2019-09-09 12:41:04 -04:00

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// 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_