std::piecewise_constant_distribution

std::piecewise_constant_distribution - cppreference.com

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`template< class RealType = double > class piecewise_constant_distribution;`		(since C++11)

std::piecewise_constant_distribution produces random floating-point numbers, which are uniformly distributed within each of the several subintervals [bi, bi+1), each with its own weight wi. The set of interval boundaries and the set of weights are the parameters of this distribution.

The probability density for any bi ≤ x <bi+1 is

, 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` (C++11)	`RealType`
`param_type` (C++11)	the type of the parameter set, see RandomNumberDistribution.

Member functions

(constructor) (C++11)	constructs new distribution (public member function) [edit]
reset (C++11)	resets the internal state of the distribution (public member function) [edit]
Generation
operator() (C++11)	generates the next random number in the distribution (public member function) [edit]
Characteristics
intervalsdensities	returns the distribution parameters (public member function) [edit]
param (C++11)	gets or sets the distribution parameter object (public member function) [edit]
min (C++11)	returns the minimum potentially generated value (public member function) [edit]
max (C++11)	returns the maximum potentially generated value (public member function) [edit]

Non-member functions

Example

#include <iostream>
#include <map>
#include <random>
#include <string>

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 {}; n < 1e4; ++n)
        ++hist[d(gen)];

    for (std::cout << std::hex << std::uppercase; auto [x, y] : hist)
        std::cout << x << ' ' << std::string(y / 100, '*') << '\n';
}

Possible output:

0 **************************************************
A **********
B *********
C *********
D **********
E *********

References

C++23 standard (ISO/IEC 14882:2024):

28.5.9.6.2 Class template piecewise_constant_distribution [rand.dist.samp.pconst] (p: 1421-1422)

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)