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)