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.
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
#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:
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