std::iterator
Defined in header <iterator> | ? | ? |
|---|---|---|
template< class Category, class T, class Distance = std::ptrdiff_t, class Pointer = T*, class Reference = T& > struct iterator; | ? | (deprecated in C++17) |
std::iterator为简化迭代器所需类型的定义而提供的基类。
模板参数
Category | - | the category of the iterator. Must be one of iterator category tags. |
|---|---|---|
T | - | the type of the values that can be obtained by dereferencing the iterator. This type should be void for output iterators. |
Distance | - | a type that can be used to identify distance between iterators |
Pointer | - | defines a pointer to the type iterated over (T) |
Reference | - | defines a reference to the type iterated over (T) |
成员类型
Member type | Definition |
|---|---|
iterator_category | Category |
value_type | T |
difference_type | Distance |
pointer | Pointer |
reference | Reference |
例
下面的示例演示如何实现输入迭代器通过从std：：iterator继承。
二次
#include <iostream>
#include <algorithm>
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 a 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';
}二次
产出：
二次
18
3 4 5二次
另见
iterator_traits | provides uniform interface to the properties of an iterator (class template) |
|---|---|
input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tag | empty class types used to indicate iterator categories (class) |
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