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std::piecew...istribution(3) C++ Standard Libary std::piecew...istribution(3) NAME std::piecewise_constant_distribution - std::piecewise_constant_distrib- ution Synopsis Defined in header <random> template< class RealType = double > (since C++11) class piecewise_constant_distribution; std::piecewise_constant_distribution produces random floating-point numbers, which are uniformly distributed within each of the several subintervals [b i, b i+1), each with its own weight w i. The set of interval boundaries and the set of weights are the pa- rameters of this distribution. The probability density for any b ix<b i+1 is w i S (b i+1 - b i) . where S is the sum of all weights. std::piecewise_constant_distribution satisfies all requirements of RandomNumberDistribution Template parameters RealType - The result type generated by the generator. The effect is undefined if this is not one of float, double, or long double. Member types Member type Definition result_type RealType param_type(C++11) the type of the parameter set, see RandomNum- berDistribution. Member functions constructor constructs new distribution (C++11) (public member function) reset resets the internal state of the distribution (C++11) (public member function) Generation operator() generates the next random number in the distribution (C++11) (public member function) Characteristics intervals returns the distribution parameters densities (public member function) param gets or sets the distribution parameter object (C++11) (public member function) min returns the minimum potentially generated value (C++11) (public member function) max returns the maximum potentially generated value (C++11) (public member function) Non-member functions operator== operator!= compares two distribution objects (C++11) (function) (C++11)(removed in C++20) operator<< performs stream input and output on pseudo-random number operator>> distribution (C++11) (function template) Example // Run this code #include <iostream> #include <string> #include <map> #include <random> int main() { std::random_device rd; std::mt19937 gen(rd()); // 50% of the time, generate a random number between 0 and 1 // 50% of the time, generate a random number between 10 and 15 std::vector<double> i{0, 1, 10, 15}; std::vector<double> w{ 1, 0, 1 }; std::piecewise_constant_distribution<> d(i.begin(), i.end(), w.be- gin()); std::map<int, int> hist; for(int n=0; n<10000; ++n) { ++hist[d(gen)]; } for(auto p : hist) { std::cout << std::hex << std::uppercase << p.first << ' ' << std::string(p.second/100, '*') << '\n'; } } Possible output: 0 ************************************************** A ********** B ********* C ********* D ********** E ********* References * C++20 standard (ISO/IEC 14882:2020): * 29.6.9.6.2 Class template piecewise_constant_distribu- tion [rand.dist.samp.pconst] (p: 1207-1208) * C++17 standard (ISO/IEC 14882:2017): * 29.6.8.6.2 Class template piecewise_constant_distribu- tion [rand.dist.samp.pconst] (p: 1098-1100) * C++14 standard (ISO/IEC 14882:2014): * 26.5.8.6.2 Class template piecewise_constant_distribu- tion [rand.dist.samp.pconst] (p: 962-964) * C++11 standard (ISO/IEC 14882:2011): * 26.5.8.6.2 Class template piecewise_constant_distribu- tion [rand.dist.samp.pconst] (p: 955-957) http://cppreference.com 2022.07.31 std::piecew...istribution(3)
NAME | Synopsis | Template parameters | Member types | Member functions | Generation | Characteristics | Non-member functions | Example | Possible output: | References
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