C++ 概念： RandomAccessIterator

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C++
 
C++ 的概念
基础
库
NullablePointer（C++11）
Hash（C++11）
Allocator
容器
容器元素
CopyInsertable（C++11）
MoveInsertable（C++11）
迭代器
ForwardIterator
BidirectionalIterator
RandomAccessIterator
随机数
SeedSequence（C++11）
RandomNumberEngine（C++11）
并发
BasicLockable（C++11）
Lockable（C++11）
TimedLockable（C++11）
Mutex（C++11）
TimedMutex（C++11）
其它
UnaryTypeTrait（C++11）
BinaryTypeTrait（C++11）
TransformationTrait（C++11）
TrivialClock（C++11）
 
一个RandomAccessIterator是一个可移动的BidirectionalIterator指向任何元素在固定的时间.
Original:
A RandomAccessIterator is a BidirectionalIterator that can be moved to point to any element in constant time.
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一个标准的指针是一个类型，满足这个概念的一个例子.
Original:
A standard pointer is an example of a type that satisfies this concept.
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[编辑] 要求

除上述要求外，类型ItRandomAccessIterator，实例a，b，i和rIt必须：
Original:
In addition to the above requirement, for a type It to be an RandomAccessIterator, instances a, b, i, and r of It must:
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Expression Return Equivalent expression Notes
r += n It& if(n>=0)

   while(n--) ++r;
else
   while(n++) --r;
return r;

  • n既可以是正的或负的
    Original:
    n can be both positive or negative
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  • 常量复杂度（即，相当于表达式不能被用作实施）
    Original:
    Constant complexity (that is, the equivalent expression cannot be used as implementation)
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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 < a)
  • 如果a < b然后!(b < a)
    Original:
    if a < b then !(b < a)
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  • 如果a < bb < c然后a < c
    Original:
    if a < b and b < c then a < c
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  • a < b或b < a或a == b
    （正是其中的一个表达式为true）
    Original:
    a < b or b < a or a == b
    (exactly one of the expressions is true)
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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
    Original:
    It is the type implementing this concept
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  • T是类型std::iterator_traits<It>::value_type
    Original:
    T is the type std::iterator_traits<It>::value_type
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  • reference是类型std::iterator_traits<It>::reference
    Original:
    reference is the type std::iterator_traits<It>::reference
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  • difference是类型std::iterator_traits<It>::difference_type
    Original:
    difference is the type std::iterator_traits<It>::difference_type
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  • i，a，b类型的对象It或const It
    Original:
    i, a, b are objects of type It or const It
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  • r是一个值类型It&
    Original:
    r is a value of type It&
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  • n是的整数类型difference
    Original:
    n is an integer of type difference
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上述规则意味着RandomAccessIterator的实现LessThanComparable.
Original:
The above rules imply that RandomAccessIterator also implements LessThanComparable.
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一个mutable RandomAccessiterator是一个BidirectionalIterator，另外满足OutputIterator要求的.
Original:
A mutable RandomAccessiterator is a BidirectionalIterator that additionally satisfies the OutputIterator requirements.
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来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/concept/RandomAccessIterator&oldid=26738”