C++ 概念: RandomAccessIterator
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一个
RandomAccessIterator
是一个可移动的BidirectionalIterator
指向任何元素在固定的时间.原文:
A
RandomAccessIterator
is a BidirectionalIterator
that can be moved to point to any element in constant time.一个标准的指针是一个类型,满足这个概念的一个例子.
原文:
A standard pointer is an example of a type that satisfies this concept.
[编辑] 要求
除上述要求外,类型
It
RandomAccessIterator
,实例a
,b
,i
和r
It
必须:原文:
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; |
|
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; |
|
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 > 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) |
[编辑] 表注意事项
It
是实现这一概念的类型原文:It
is the type implementing this conceptreference
是类型std::iterator_traits<It>::reference原文:reference
is the type std::iterator_traits<It>::referencedifference
是类型std::iterator_traits<It>::difference_type原文:difference
is the type std::iterator_traits<It>::difference_typei
,a
,b
类型的对象It
或const It
原文:i
,a
,b
are objects of typeIt
orconst It
n
是的整数类型difference
上述规则意味着RandomAccessIterator的实现
LessThanComparable
.原文:
The above rules imply that RandomAccessIterator also implements
LessThanComparable
.一个
mutable RandomAccessiterator
是一个BidirectionalIterator
,另外满足OutputIterator
要求的.原文:
A
mutable RandomAccessiterator
is a BidirectionalIterator
that additionally satisfies the OutputIterator
requirements.