Namespaces
Variants

std:: iterator

From cppreference.net
C++
Iterator library
Iterator concepts
Iterator primitives
iterator
(deprecated in C++17)
(C++20)
(C++20)


Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Range access
(C++11) (C++14)
(C++14) (C++14)
(C++11) (C++14)
(C++14) (C++14)
(C++17) (C++20)
(C++17)
(C++17)
定义于头文件 <iterator>
template <

class Category,
class T,
class Distance = std:: ptrdiff_t ,
class Pointer = T * ,
class Reference = T &

> struct iterator ;
(C++17 起已弃用)

std::iterator 是为简化迭代器所需类型定义而提供的基类。

目录

模板参数

Category - 迭代器的类别。必须是 迭代器类别标签 之一。
T - 通过解引用迭代器可获取的值的类型。对于输出迭代器，此类型应为 void 。
Distance - 可用于标识迭代器间距离的类型
Pointer - 定义指向迭代类型（ T ）的指针
Reference - 定义指向迭代类型（ T ）的引用

成员类型

成员类型 定义
iterator_category Category
value_type T
difference_type Distance
pointer Pointer
reference Reference

示例

以下示例展示了如何通过继承 std::iterator 来实现 输入迭代器

运行此代码 
#include <algorithm>
#include <iostream>
template<long FROM, long TO>
class Range
{
public:
    // member typedefs provided through inheriting from std::iterator
    class iterator : public std::iterator<
                                std::input_iterator_tag, // iterator_category
                                long,                    // value_type
                                long,                    // difference_type
                                const long*,             // pointer
                                long                     // reference
                            > {
        long num = FROM;
    public:
        explicit iterator(long _num = 0) : num(_num) {}
        iterator& operator++() { num = TO >= FROM ? num + 1: num - 1; return *this; }
        iterator operator++(int) { iterator retval = *this; ++(*this); return retval; }
        bool operator==(iterator other) const { return num == other.num; }
        bool operator!=(iterator other) const { return !(*this == other); }
        reference operator*() const { return num; }
    };
    iterator begin() { return iterator(FROM); }
    iterator end() { return iterator(TO >= FROM? TO + 1 : TO - 1); }
};
int main()
{
    // std::find requires an input iterator
    auto range = Range<15, 25>();
    auto itr = std::find(range.begin(), range.end(), 18);
    std::cout << *itr << '\n'; // 18
    // Range::iterator also satisfies range-based for requirements
    for (long l : Range<3, 5>())
        std::cout << l << ' '; // 3 4 5
    std::cout << '\n';
}

输出： 

18
3 4 5

参见

为迭代器的属性提供统一接口
(类模板)
(C++20)
用于指示迭代器类别的空类类型
(类)