C++ concepts: RandomAccessIterator

 

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C++ concepts

Basic
DefaultConstructible CopyAssignable CopyConstructible	MoveAssignable (C++11) MoveConstructible (C++11) Destructible
Library-Wide
EqualityComparable LessThanComparable Swappable (C++11) ValueSwappable (C++11)	NullablePointer (C++11) Hash (C++11) Allocator
Container
Container SequenceContainer ReversibleContainer	AssociativeContainer AllocatorAwareContainer UnorderedAssociativeContainer (C++11)
Container Elements
CopyInsertable (C++11) MoveInsertable (C++11)	EmplaceConstructible (C++11)
Iterator
Iterator OutputIterator InputIterator	ForwardIterator BidirectionalIterator RandomAccessIterator
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++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 standard pointer is an example of a type that satisfies this concept.

Requirements

• BidirectionalIterator

In addition to the above requirement, for a type It to be an RandomAccessIterator, instances a, b, i, and r of It must:

Expression	Return	Equivalent expression	Notes
r += n	It&	if ( n >= 0 )    while(n--) ++r; else    while(n++) --r; return r;	n can be both positive or negative Constant complexity (that is, the equivalent expression cannot be used as implementation)
i + n	It	It temp = i; return temp += n;
n + i	It	i + n
r -= n	It&	return r += -n;
i - n	It	It temp = i; return temp -= n;
b - a	difference	n	returns n such that a + n == b, where 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)

Table Notes

• It is the type implementing this concept
• T is the type std::iterator_traits<It>::value_type
• reference is the type std::iterator_traits<It>::reference
• difference is the type std::iterator_traits<It>::difference_type
• i, a, b are objects of type It or const It
• r is a value of type It&
• n is an integer of type difference

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