78 lines
2.4 KiB
C++
78 lines
2.4 KiB
C++
/* @file engine_concept.hpp */
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#pragma once
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#include <concepts>
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#include <random>
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namespace std {
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#ifdef __clang__
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# if __clang_major__ <= 11
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template < class T >
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concept integral = std::is_integral_v<T>;
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template < class T >
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concept signed_integral = std::integral<T> && std::is_signed_v<T>;
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template < class T >
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concept unsigned_integral
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= std::integral<T> && !std::signed_integral<T>;
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template< class F, class... Args >
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concept invocable
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= requires(F&& f, Args&&... args) {
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std::invoke(std::forward<F>(f), std::forward<Args>(args)...);
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/* not required to be equality-preserving */
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};
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template< typename G >
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concept uniform_random_bit_generator
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= std::invocable<G&>
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&& std::unsigned_integral<std::invoke_result_t<G&>>
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&& requires { { G::min() } -> std::same_as<std::invoke_result_t<G&>>;
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{ G::max() } -> std::same_as<std::invoke_result_t<G&>>;
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requires std::bool_constant<(G::min() < G::max())>::value; };
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# endif
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#else
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/* uniform_random_bit_generator provided by gcc 12.3.2 */
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/* uniform_random_bit_generator provided by clang 16 */
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#endif
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} /*namespace std*/
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namespace xo {
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namespace rng {
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/* an engine generates psuedo-random bits.
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* given
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* RngEngine eng = ...;
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*
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* RngEngine::result_type x = eng();
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*
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* puts random bits into x.
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*/
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template <class RngEngine>
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concept engine_concept = requires(RngEngine engine, typename RngEngine::result_type r) {
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/* note: the first 4 requirements characterize UniformRandomBitGenerator */
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typename RngEngine::result_type;
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{ RngEngine(r) };
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{ engine.min() } -> std::same_as<typename RngEngine::result_type>;
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{ engine.max() } -> std::same_as<typename RngEngine::result_type>;
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/* must return value in closed interval [.min(), .max()] */
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{ engine() } -> std::same_as<typename RngEngine::result_type>;
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{ engine.seed() };
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{ engine.seed(r) };
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{ engine == engine };
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{ engine != engine };
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}
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#ifdef __clang__
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// std::copyable apparently not available in clang11 ?
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#else
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&& std::copyable<RngEngine>
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#endif
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&& std::uniform_random_bit_generator<RngEngine>;
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} /*namespace rng*/
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} /*namespace xo*/
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/* end engine_concept.hpp */
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