std::piecewise_constant_distribution(3)

NAME
std::piecewise_constant_distribution - std::piecewise_constant_distribution

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 parameters of this
   distribution.
   The probability density for any b
   i≤x<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 RandomNumberDistribution.

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.begin());
     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_distribution
                [rand.dist.samp.pconst] (p: 1207-1208)
     * C++17 standard (ISO/IEC 14882:2017):
              * 29.6.8.6.2 Class template piecewise_constant_distribution
                [rand.dist.samp.pconst] (p: 1098-1100)
     * C++14 standard (ISO/IEC 14882:2014):
              * 26.5.8.6.2 Class template piecewise_constant_distribution
                [rand.dist.samp.pconst] (p: 962-964)
     * C++11 standard (ISO/IEC 14882:2011):
              * 26.5.8.6.2 Class template piecewise_constant_distribution
                [rand.dist.samp.pconst] (p: 955-957)