libcruft-util/random.hpp
Danny Robson 107947899c random: remove generator choice from easy API
it's supposed to be an easy replacement for std::rand, we don't need to
let the user choose their generator.
2017-08-28 14:12:36 +10:00

67 lines
2.0 KiB
C++

/*
* 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
*
* http://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.
*
* Copyright 2016 Danny Robson <danny@nerdcruft.net>
*/
#ifndef CRUFT_UTIL_RANDOM_HPP
#define CRUFT_UTIL_RANDOM_HPP
#include <random>
namespace util::random {
///////////////////////////////////////////////////////////////////////////
/// return correctly initialised thread-local generator of an unspecified,
/// but not entirely useless, type. ie, not LCG.
auto&
generator (void)
{
static thread_local std::mt19937_64 gen { std::random_device {}() };
return gen;
}
///////////////////////////////////////////////////////////////////////////
/// select a value uniformly from the range [lo, hi)
template <typename T>
std::enable_if_t<std::is_floating_point_v<T>,T>
uniform (T lo, T hi)
{
return std::uniform_real_distribution { lo, hi } (generator ());
}
//-------------------------------------------------------------------------
/// select a value uniformly from the range [lo, hi)
template <typename T>
std::enable_if_t<std::is_integral_v<T>,T>
uniform (T lo, T hi)
{
return std::uniform_int_distribution { lo, hi } (generator ());
}
///////////////////////////////////////////////////////////////////////////
/// choose a value at random from an array
template <typename T, size_t N>
T&
choose (T (&t)[N])
{
std::uniform_int_distribution<size_t> dist (0, N - 1);
return t[dist (generator ())];
}
}
#endif