class
<random>
std::random_device
True random number generator
A random number generator that produces non-deterministic random numbers, if supported.
Unlike the other standard generators, this is not meant to be an engine that generates pseudo-random numbers, but a generator based on stochastic processes to generate a sequence of uniformly distributed random numbers. Although, certain library implementations may lack the ability to produce such numbers and employ a random number engine to generate pseudo-random values instead. In this case, entropy returns zero.
Notice that random devices may not always be available to produce random numbers (and in some systems, they may even never be available). This is signaled by throwing an exception derived from the standard exception on construction or when a number is requested with operator().
Unless the program really requires a stochastic process to generate random numbers, a portable program is encouraged to use an alternate pseudo-random number generator engine instead, or at least provide a recovery method for such exceptions.
Member types
The following alias is a member type of random_device:
| member type | definition | notes |
|---|
| result_type | unsigned int | The type of the numbers generated. |
Member functions
- (constructor)
- Construct random device (public member function)
- min
- Minimum value (public static member function)
- max
- Maximum value (public static member function)
- operator()
- Generate random number (public member function)
- entropy
- Return entropy (public member function)