A random number engine is a function object returning unsigned integer values such that each value in the range of possible results has (ideally) equal probability.
Any random number engine is also a UniformRandomBitGenerator, and therefore may be plugged into any random number distribution in order to obtain a random number (formally, a random variate).
A type E
satisfying UniformRandomBitGenerator will additionally satisfy RandomNumberEngine if, given.
T
, the type named by E::result_type
s
, a value of type T
e
, a non-const value of type E
v
, an lvalue of type E
x
and y
, possibly const values of type E
q
, a lvalue of some type satisfying SeedSequence z
, a value of type unsigned long long
os
, an output stream is
, an input stream the following expressions are valid and have their specified effects:
Expression | Return type | Requirements |
---|---|---|
E() | Creates an engine with the same state as all other default-constructed engines of type E . |
|
E(x) | Creates an engine with the same state as x . |
|
E(s) | Creates an engine whose initial state is determined by the integer s . |
|
E(q) | Creates an engine whose initial state is determined by a single call to q.generate . |
|
e.seed() | void | Sets e == E() . |
e.seed(s) | void | Sets e == E(s) . |
e.seed(q) | void | Sets e == E(q) . |
e() | T | Returns a value in the closed interval [E::min(), E::max()] . Has amortized constant complexity. |
e.discard(z) | void | Advances e 's state as if by z consecutive calls to e() . |
x == y | bool | true if x and y are in the same state (such that repeated future calls to x() and y() will produce identical sequences). Otherwise, false . |
x != y | bool | !(x == y) |
os << x | decltype(os)& | Writes to os the textual representation of x 's current state. In the output, adjacent numbers are separated by one or more space characters. If os 's fmtflags are not set to ios_base::dec|ios_base::left , the behavior may be undefined. |
is >> v | decltype(is)& | Reads from is the textual representation of v 's current state, such that if that state was previously written via os << x , then x == v . If is 's fmtflags are not set to ios_base::dec , the behavior may be undefined. |
The following standard library facilities satisfy RandomNumberEngine:
(C++11) | implements linear congruential algorithm (class template) |
(C++11) | implements Mersenne twister algorithm (class template) |
(C++11) | implements a subtract-with-carry ( lagged Fibonacci) algorithm (class template) |
(C++11) | discards some output of a random number engine (class template) |
(C++11) | packs the output of a random number engine into blocks of a specified number of bits (class template) |
(C++11) | delivers the output of a random number engine in a different order (class template) |
The following standard library facilities satisfy UniformRandomBitGenerator but not RandomNumberEngine:
(C++11) | non-deterministic random number generator using hardware entropy source (class) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/named_req/RandomNumberEngine