C++ named requirements: UniformRandomBitGenerator

 

C++

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Named requirements

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Concepts library (C++20)

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Technical Specifications

 

C++ named requirements

Basic
DefaultConstructible CopyAssignable CopyConstructible	MoveAssignable (C++11) MoveConstructible (C++11) Destructible
Layout
TrivialType (C++11) TriviallyCopyable (C++11)	StandardLayoutType (C++11) PODType
Library-Wide
EqualityComparable LessThanComparable Swappable (C++11) ValueSwappable (C++11) NullablePointer (C++11) Hash (C++11)	Allocator FunctionObject Callable Predicate BinaryPredicate Compare
Container
Container SequenceContainer ContiguousContainer (C++17) ReversibleContainer	AssociativeContainer AllocatorAwareContainer UnorderedAssociativeContainer (C++11)
Container Elements
DefaultInsertable (C++11) CopyInsertable (C++11) MoveInsertable (C++11)	EmplaceConstructible (C++11) Erasable (C++11)
Iterator
LegacyIterator LegacyOutputIterator LegacyInputIterator LegacyForwardIterator	LegacyBidirectionalIterator LegacyRandomAccessIterator LegacyContiguousIterator (C++17) ConstexprIterator (C++20)
Stream I/O
FormattedInputFunction UnformattedInputFunction	FormattedOutputFunction UnformattedOutputFunction
Random Numbers
SeedSequence (C++11) RandomNumberEngine (C++11)	RandomNumberDistribution (C++11) UniformRandomBitGenerator (C++11) RandomNumberEngineAdaptor (C++11)
Concurrency
BasicLockable (C++11) Lockable (C++11) TimedLockable (C++11)	Mutex (C++11) TimedMutex (C++11) SharedMutex (C++17) SharedTimedMutex (C++14)
Other
CharTraits RegexTraits (C++11) BitmaskType NumericType LiteralType (C++11)	UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11) Clock (C++11) TrivialClock (C++11)

 

A uniform random bit generator is a function object returning unsigned integer values such that each value in the range of possible results has (ideally) equal probability.

Uniform random bit generators are not intended to be used as random number generators: they are used as the source of random bits (generated in bulk, for efficiency). Any uniform random bit generator may be plugged into any random number distribution in order to obtain a random number (formally, a random variate).

Requirements

The type G satisfies UniformRandomBitGenerator if

Given

• T, the type named by G::result_type
• g, a value of type G

The following expressions must be valid and have their specified effects

Expression	Return type	Requirements
G::result_type	T	T is an unsigned integer type
G::min()	T	Returns the smallest value that G's operator() may return. The value is strictly less than G::max().
G::max()	T	Returns the largest value that G's operator() may return. The value is strictly greater than G::min()
g()	T	Returns a value in the closed interval [G::min(), G::max()]. Has amortized constant complexity.

Notes

All RandomNumberEngines satisfy this requirement.

Standard library

The following standard library facilities expect a UniformRandomBitGenerator type.

random_shuffleshuffle (until C++17)(C++11)	randomly re-orders elements in a range (function template)
generate_canonical (C++11)	evenly distributes real values of given precision across [0, 1) (function template)
uniform_int_distribution (C++11)	produces integer values evenly distributed across a range (class template)
uniform_real_distribution (C++11)	produces real values evenly distributed across a range (class template)
all other random number distributions

The following standard library facilities satisfy UniformRandomBitGenerator without additionally satisfying RandomNumberEngine:

random_device (C++11)

non-deterministic random number generator using hardware entropy source (class)