libcruft-util/rand/lcg.hpp

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/*
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* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
* Copyright 2015 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_RAND_LCG_HPP
#define __UTIL_RAND_LCG_HPP
#include <cstdint>
#include <type_traits>
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namespace cruft::rand {
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/// linear congruential generator
///
/// T: output/state type
/// M: modulus
/// A: multiplier
/// C: increment
template <typename T, T M, T A, T C>
struct lcg {
public:
using result_type = T;
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static_assert (std::is_unsigned<T>::value,
"LCG generates integer overflow which is undefined behaviour for signed types");
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explicit lcg (T seed);
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result_type operator() (void);
static result_type min (void);
static result_type max (void);
void discard (unsigned);
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private:
T m_x;
};
// glibc: typedef lcg<uint32_t, pow2(31), 1103515245, 12345> lcg_t;
using lcg_t = lcg<uint64_t,0u,6364136223846793005ul, 1ul>;
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}
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#endif