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
is the base class provided to simplify definitions of the required types for iterators.
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 ) |
Member type | Definition |
---|---|
iterator_category | Category |
value_type | T |
difference_type | Distance |
pointer | Pointer |
reference | Reference |
The following example shows how to implement an input iterator by inheriting from std::iterator.
#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 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'; }
Output:
18 3 4 5
provides uniform interface to the properties of an iterator (class template) |
|
(C++20) | empty class types used to indicate iterator categories (class) |
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