c ++ set ordered iterating - 迭代集合的结果，按标准排序？ [英] c++ set ordered iterating - Are results of iterating over set, ordered by standard?

问题描述

我可以依靠假设（换句话说：它是否由标准保证）：

Can I rely on the assumption (in other words: Is it guaranteed by standard?) that :

• set< T> :: begin（）将指向集合中的最小元素。


• 迭代集合， ; T> :: begin（）直到 set< T> :: end（））将按递增顺序给出元素


• 并确保： map ？

• set<T>::begin() will point to the smallest element in set?
• iterating over set, (from set<T>::begin() till set<T>::end()) will give elements in increasing order?
• and just to be sure: Do these properties hold for keys in map?

我是指设置和映射从 STL 。

PS我知道邻接运算符<（）并定义自己的比较器。

P.S. I know abut operator<() and defining own comparators. Please ensure me about what standard says about this ?

推荐答案

是的，你可以依赖定义，这取决于元素的键） bool operator< 或作为模板参数传递给集合（映射）的比较函子。因此，根据所使用的比较器，排序将从最小到最大。

Yes, you can rely on that by definition, depending on the element's (keys) bool operator< or the comparison functor passed as template parameter to the set (map). So the ordering will be from smallest to largest according to the comparator used.

在C ++ 11标准§23.2.4中，处理关联容器的要求：

In the C++11 standard, §23.2.4, dealing with requirements of Associative Containers:

每个关联容器都在Key和一个排序关系比较中参数化，从而在Key的元素上引入严格的弱排序（25.4）。此外，地图和多重映射将任意类型T与密钥相关联。比较类型的对象称为容器的比较对象。

Each associative container is parameterized on Key and an ordering relation Compare that induces a strict weak ordering (25.4) on elements of Key. In addition, map and multimap associate an arbitrary type T with the Key. The object of type Compare is called the comparison object of a container.

然后，在同一节中：

关联容器的迭代器的基本属性是它们以键的非降序顺序遍历容器
，其中非降序由用于
的比较构造它们。对于任何两个可解引用迭代器i和j，使得从i到j的距离为正，
value_comp（* j，* i）== false

The fundamental property of iterators of associative containers is that they iterate through the containers in the non-descending order of keys where non-descending is defined by the comparison that was used to construct them. For any two dereferenceable iterators i and j such that distance from i to j is positive, value_comp(*j, *i) == false

b $ b

其中 value_comp 是比较函数。

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