std::piecewise_constant_distribution

 

C++

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Technical Specifications

 

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discrete_distribution (C++11)

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C library

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std::piecewise_constant_distribution

Member functions

piecewise_constant_distribution::piecewise_constant_distribution

piecewise_constant_distribution::reset

Generation

piecewise_constant_distribution::operator()

Characteristics

piecewise_constant_distribution::intervalspiecewise_constant_distribution::densities

piecewise_constant_distribution::param

piecewise_constant_distribution::min

piecewise_constant_distribution::max

Non-member functions

operator==operator!=

operator<<operator>>

 

Defined in header <random>
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 [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 k

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	the type of the parameter set, see RandomNumberDistribution.

Member functions

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

Non-member functions

operator==operator!=	compares two distribution objects (function)
operator<<operator>>	performs stream input and output on pseudo-random number distribution (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 << p.first << ' ' << std::string(p.second/100, '*') << '\n';
    }
}

Output:

0 **************************************************
10 **********
11 *********
12 *********
13 **********
14 *********