cpp/named req/RandomAccessIterator

A RandomAccessIterator is a Template:concept 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

• Template:concept

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 i += n;
n + i	It	i + n
r -= n	It&	return r += -n;
i - n	It	It temp = i; return i -= n;
n - i	It	i - n
b - a	difference	n	returns n such that a+n==b
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 Template:concept.