std::iterator
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iterator
(deprecated in C++17)
(C++20)
(C++20)
(C++20)(C++20)
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Defined in header
<iterator>
template<
(deprecated in C++17)
class Category,
class T,
class Distance = std::ptrdiff_t,
class Pointer = T*,
class Reference = T&
std::iterator is the base class provided to simplify definitions of the required types for iterators.
[edit] Template parameters
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)
[edit] Member types
Member type
Definition
iterator_category
Category
value_type
T
difference_type
Distance
pointer
Pointer
reference
Reference
[edit] Example
The following example shows how to implement an input iterator by inheriting from std::iterator
Run this code
#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'; }
Output:
18 3 4 5