C++

Reference

<random>

discrete_distribution

class template
<random>

std::discrete_distribution

template <class IntType = int> class discrete_distribution;
Discrete distribution
Random number distribution that produces integer values according to a discrete distribution, where each possible value has a predefined probability of being produced:



The w's are a set of n non-negative individual weights set on construction (or using member param). The probability of each of the n possible numbers to be produced being their corresponding weight divided by the total of all weights.

To produce a random value following this distribution, call its member function operator().

Template parameters

IntType
An integer type. Aliased as member type result_type.
By default, this is int.

Member types

The following aliases are member types of discrete_distribution:

member typedefinitionnotes
result_typeThe first template parameter (IntType)The type of the numbers generated (defaults to int)
param_typenot specifiedThe type returned by member param.

Member functions

(constructor)
Construct discrete distribution (public member function)
operator()
Generate random number (public member function)
reset
Reset distribution (public member function)
param
Distribution parameters (public member function)
min
Minimum value (public member function)
max
Maximum value (public member function)

Distribution parameters:

probabilities
Probabilities (public member function)

Non-member functions

operator<<
Insert into output stream (function template)
operator>>
Extract from input stream (function template)
relational operators
Relational operators (function template)

Example

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// discrete_distribution
#include <iostream>
#include <random>

int main()
{
  const int nrolls = 10000; // number of experiments
  const int nstars = 100;   // maximum number of stars to distribute

  std::default_random_engine generator;
  std::discrete_distribution<int> distribution {2,2,1,1,2,2,1,1,2,2};

  int p[10]={};

  for (int i=0; i<nrolls; ++i) {
    int number = distribution(generator);
    ++p[number];
  }

  std::cout << "a discrete_distribution:" << std::endl;
  for (int i=0; i<10; ++i)
    std::cout << i << ": " << std::string(p[i]*nstars/nrolls,'*') << std::endl;

  return 0;
}

Possible output:
a discrete_distribution:
0: ************
1: *************
2: *****
3: ******
4: ************
5: ************
6: ******
7: ******
8: ************
9: ************


See also

uniform_int_distribution
Uniform discrete distribution (class template)
piecewise_constant_distribution
Piecewise constant distribution (class template)