C++ concepts: RandomAccessIterator

 

C++

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Technical Specifications

 

C++ concepts

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
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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
Iterator OutputIterator InputIterator	ForwardIterator BidirectionalIterator RandomAccessIterator ContiguousIterator (C++17)
Stream I/O
FormattedInputFunction UnformattedInputFunction	FormattedOutputFunction UnformattedOutputFunction
Random Numbers
SeedSequence (C++11) RandomNumberEngine (C++11)	RandomNumberDistribution (C++11) UniformRandomNumberGenerator (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 pos_type off_type Clock (C++11) BitmaskType	UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11) TrivialClock (C++11) LiteralType (C++11)

 

A RandomAccessIterator is a BidirectionalIterator that can be moved to point to any element in constant time.

A pointer to an element of an array satisfies all requirements of RandomAccessIterator

Requirements

The type It satisfies RandomAccessIterator if

• The type It satisfies BidirectionalIterator

And, given

• value_type, the type denoted by std::iterator_traits<It>::value_type
• difference_type, the type denoted by std::iterator_traits<It>::difference_type
• reference, the type denoted by std::iterator_traits<It>::reference
• i, a, b, objects of type It or const It
• r, a value of type It&
• n, an integer of type difference_type

The following expressions must be valid and have their specified effects

Expression	Return type	Operational semantics	Notes
r += n	It&	difference_type m = n; if (m >= 0) while (m--) ++r; else while (m++) --r; return r;	n can be both positive or negative The complexity is constant (that is, the implementation cannot actually execute the while loop shown in operational semantics)
a + n n + a	It	It temp = a; return temp += n;	n can be both positive or negative a + n == n + a
r -= n	It&	return r += -n;
i - n	It	It temp = i; return temp -= n;
b - a	difference_type	return n;	Precondition: there exists a value n of type difference_type such that a+n==b Postcondition: b == a + (b - a).
i[n]	convertible to reference	*(i + n)
a < b	contextually convertible to bool	b - a > 0	Strict total ordering relation: !(a < a) if a < b then !(b < a) if a < b and b < c then a < c a < b or b < a or a == b (exactly one of the expressions is true)
a > b	contextually convertible to bool	b < a	Total ordering relation opposite to a < b
a >= b	contextually convertible to bool	!(a < b)
a <= b	contextually convertible to bool	!(a > b)

The above rules imply that RandomAccessIterator also implements LessThanComparable.

A mutable RandomAccessIterator is a RandomAccessIterator that additionally satisfies the OutputIterator requirements.

See also

• Iterator library