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std::random_device

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< cpp‎ | numeric‎ | random
Revision as of 17:30, 9 July 2013 by P12bot (Talk | contribs)

 
 
 
 
 
Defined in header <random>
class random_device;
(since C++11)

std::random_device is a uniformly-distributed integer random number generator that produces non-deterministic random numbers.

Note that std::random_device may be implemented in terms of a pseudo-random number engine if a non-deterministic source (e.g. a hardware device) is not available to the implementation.

Contents

Member types

Member type Definition
result_type unsigned int

Member functions

Construction
constructs the engine
(public member function) [edit]
operator=
(deleted)
the assignment operator is deleted
(public member function)
Generation
advances the engine's state and returns the generated value
(public member function) [edit]
Characteristics
obtains the entropy estimate for the non-deterministic random number generator
(public member function) [edit]
[static]
gets the smallest possible value in the output range
(public static member function) [edit]
[static]
gets the largest possible value in the output range
(public static member function) [edit]

Example

#include <iostream>
#include <string>
#include <map>
#include <random>
 
int main()
{
    std::random_device rd;
    std::map<int, int> hist;
    std::uniform_int_distribution<int> dist(0, 9);
    for (int n = 0; n < 20000; ++n) {
        ++hist[dist(rd)];
    }
    for (auto p : hist) {
        std::cout << p.first << " : " << std::string(p.second/100, '*') << '\n';
    }
}

Possible output:

0 : ********************
1 : *******************
2 : ********************
3 : ********************
4 : ********************
5 : *******************
6 : ********************
7 : ********************
8 : *******************
9 : ********************