std::subtra...carry_engine(3) C++ Standard Libary std::subtra...carry_engine(3) NAME std::subtract_with_carry_engine - std::subtract_with_carry_engine Synopsis Defined in header <random> template< class UIntType, (since C++11) std::size_t w, std::size_t s, std::size_t r > class subtract_with_carry_engine; Is a random number engine that uses subtract with carry algorithm. Template parameters The result type generated by the generator. The effect is un- defined if UIntType - this is not one of unsigned short, unsigned int, unsigned long, or unsigned long long. w - the word size, in bits, of the state sequence s - the short lag r - the long lag If w is not in [1, std::numeric_limits<UIntType>::digits], or s is not in [1, r), the program is ill-formed. Generator properties The size of the states of subtract_with_carry_engine is \(O(r)\)O(r), each of them consists of two parts: * A sequence X of r integer values, where each value is in [0, 2w ). * An integer c (known as the carrya), whose value is either 0 or 1. Given that \(X_j\)X j stands for the \(j\mod r\)j mod rth value (starting from 0) of X, the transition algorithm of subtract_with_carry_engine (\(TA(x_i)\)TA(x i)) is defined as follows: 1. Let Y be \(X_{i-s}-X_{i-r}-c\)X i-s-X i-r-c. 2. Let y be \(Y\mod 2^w\)Y mod 2w , and set \(X_i\)X i to y. 3. If Y is negative, set c to 1, otherwise set c to 0. The generation algorithm of subtract_with_carry_engine is \(GA(x_i) = y\)GA(x i) = y, where y is the value produced in step 2 of the transition algo- rithm. Predefined specializations The following specializations define the random number engine with two commonly used parameter sets: Defined in header <random> Type Definition ranlux24_base std::subtract_with_carry_engine<std::uint_fast32_t, 24, 10, (C++11) 24> ranlux48_base std::subtract_with_carry_engine<std::uint_fast64_t, 48, 5, (C++11) 12> Nested types Type Definition result_type UIntType Data members constexpr std::size_t word_size w [static] (public static member con- stant) constexpr std::size_t short_lag s [static] (public static member con- stant) constexpr std::size_t long_lag r [static] (public static member con- stant) constexpr std::uint_least32_t default_seed 19780503u [static] (public static member con- stant) Member functions Construction and Seeding constructor constructs the engine (C++11) (public member function) seed sets the current state of the engine (C++11) (public member function) Generation operator() advances the engine's state and returns the generated value (C++11) (public member function) discard advances the engine's state by a specified amount (C++11) (public member function) Characteristics min gets the smallest possible value in the output range [static] (C++11) (public static member function) max gets the largest possible value in the output range [static] (C++11) (public static member function) Non-member functions operator== compares the internal states of two pseudo- random number operator!= engines (C++11) (function) (C++11)(removed in C++20) operator<< performs stream input and output on pseudo- random number operator>> engine (C++11) (function template) Example This section is incomplete Reason: no example Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 3809 C++11 default_seed might not be changed its type to representable with result_type std::uint_least32_t Category: * Todo no example http://cppreference.com 2024.06.10 std::subtra...carry_engine(3)
NAME | Synopsis | Template parameters | Member functions | Construction and Seeding | Generation | Characteristics | Non-member functions | Example | Category:
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