class template
<random>
std::piecewise_constant_distribution
template <class RealType = double> class piecewise_constant_distribution;
Piecewise constant distribution
Random number distribution that produces floating-point values that are uniformly distributed over each of a sequence of contiguous subintervals, as defined by the following probability density function:
A set of n non-negative individual weights (the w's) for each of the subintervals [bi,bi+1) are set on construction. The probability of producing a value within each subinterval being their corresponding weight (wi) divided by the total of all weights.
To produce a random value following this distribution, call its member function operator().
Template parameters
- RealType
- A floating-point type. Aliased as member type result_type.
By default, this is double.
Member types
The following aliases are member types of piecewise_constant_distribution:
| member type | definition | notes |
|---|
| result_type | The first template parameter (RealType) | The type of the numbers generated (defaults to double) |
| param_type | not specified | The type returned by member param. |
Member functions
- (constructor)
- Construct piecewise constant 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:
- intervals
- Intervals (public member function)
- densities
- Densities (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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
// piecewise_constant_distribution
#include <iostream>
#include <array>
#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::array<double,6> intervals {0.0, 2.0, 4.0, 6.0, 8.0, 10.0};
std::array<double,5> weights {2.0, 1.0, 2.0, 1.0, 2.0};
std::piecewise_constant_distribution<double>
distribution (intervals.begin(),intervals.end(),weights.begin());
int p[10]={};
for (int i=0; i<nrolls; ++i) {
int number = distribution(generator);
++p[number];
}
std::cout << "a piecewise_constant_distribution:" << std::endl;
for (int i=0; i<10; ++i) {
std::cout << i << "-" << i+1 << ": ";
std::cout << std::string(p[i]*nstars/nrolls,'*') << std::endl;
}
return 0;
}
Possible output:
a piecewise_constant_distribution:
0-1: ************
1-2: *************
2-3: *****
3-4: ******
4-5: ************
5-6: ************
6-7: ******
7-8: ******
8-9: ************
9-10: ************