C++ named requirements: RangeAdaptorClosureObject (since C++20)

 

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C++ named requirements

Basic DefaultConstructible MoveConstructible (C++11) CopyConstructible CopyAssignable MoveAssignable (C++11) Destructible Type properties ScalarType PODType TriviallyCopyable (C++11) TrivialType (C++11) StandardLayoutType (C++11)   ImplicitLifetimeType Library-wide BooleanTestable EqualityComparable LessThanComparable Swappable ValueSwappable (C++11) NullablePointer (C++11) Hash (C++11) Allocator FunctionObject Callable Predicate BinaryPredicate Compare

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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) Multidimensional View LayoutMapping (C++23) LayoutMappingPolicy (C++23) AccessorPolicy (C++23) 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)

 

Range adaptor closure objects are FunctionObjects that are callable via the pipe operator: if C is a range adaptor closure object and R is a range, these two expressions are equivalent:

C(R)
R | C

Two range adaptor closure objects can be chained by operator| to produce another range adaptor closure object: if C and D are range adaptor closure objects, then C | D produces a range adaptor closure object E with the following properties:

• E stores a copy of C and D, direct-non-list-initialized from std::forward<decltype((C))>(C) and std::forward<decltype((D))>(D) respectively. If such initialization is invalid, C | D is also invalid.
• Let c and d be the stored copies (with the same constness and value category as E), and R be a range object, the following expressions are equivalent:

d(c(R))
R | c | d
E(R)
R | E // R | (C | D)

Notes: operator() is unsupported for volatile-qualified or const-volatile-qualified version of range adaptor object closure types.

Objects whose type is the same as one of the following objects (ignoring cv-qualification) are range adaptor closure objects:

• unary range adaptor objects,

objects of user-defined types that meet the requirements of implementing a range adaptor closure object,

(since C++23)

• the results of binding trailing arguments by range adaptor objects, and
• the results of chaining two range adaptor closure objects by operator|.

See also

ranges::range_adaptor_closure (C++23)

helper base class template for defining a range adaptor closure object (class template)