C++ named requirements: UnaryTypeTrait (since C++11)

 

C++

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Named requirements

Feature test macros (C++20)

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Concepts library (C++20)

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Strings library

Containers library

Iterators library

Ranges library (C++20)

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Technical specifications

Symbols index

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C++ named requirements

Basic
DefaultConstructible CopyAssignable	CopyConstructible MoveAssignable (C++11)	MoveConstructible (C++11) Destructible
Type properties
ScalarType TriviallyCopyable (C++11)	StandardLayoutType (C++11) PODType	TrivialType (C++11) ImplicitLifetimeType
Library-Wide
EqualityComparable LessThanComparable Swappable 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
Formatters
BasicFormatter (C++20)	Formatter (C++20)
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)	SharedLockable (C++14) SharedTimedLockable (C++14) Mutex (C++11)	TimedMutex (C++11) SharedMutex (C++17) SharedTimedMutex (C++14)
Ranges
RangeAdaptorObject (C++20)	RangeAdaptorClosureObject (C++20)
Other
CharTraits RegexTraits (C++11) BitmaskType LiteralType (C++11)	NumericType UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11)	Clock (C++11) TrivialClock (C++11)

 

A UnaryTypeTrait is a class template that describes a property of its template type parameter with an std::integral_constant (typically std::bool_constant) specialization.

Requirements

• DefaultConstructible and CopyConstructible.
• Takes one template type parameter (additional template parameters are optional and allowed).
• Publicly and unambiguously derived from a specialization of std::integral_constant, known as its base characteristic.
• The member names of the base characteristic are not hidden and are unambiguously available.

Standard library

The following type traits all satisfy UnaryTypeTrait:

• Primary type categories
• Composite type categories
• Type properties
• Supported operations
• Property queries

The following standard library class templates also satisfy UnaryTypeTrait.

integral_constant (C++11)	compile-time constant of specified type with specified value (class template)
negation (C++17)	logical NOT metafunction (class template)
std::tuple_size<std::tuple> (C++11)	obtains the size of tuple at compile time (class template specialization)
std::tuple_size<std::array> (C++11)	obtains the size of an array (class template specialization)
std::tuple_size<std::pair> (C++11)	obtains the size of a pair (class template specialization)
variant_sizevariant_size_v (C++17)	obtains the size of the variant's list of alternatives at compile time (class template) (variable template)
is_bind_expression (C++11)	indicates that an object is std::bind expression or can be used as one (class template)
is_placeholder (C++11)	indicates that an object is a standard placeholder or can be used as one (class template)
is_execution_policy (C++17)	test whether a class represents an execution policy (class template)