distance
function template
<iterator>
template<class InputIterator>
typename iterator_traits<InputIterator>::difference_type
distance (InputIterator first, InputIterator last);
Return distance between iterators
Calculates the number of elements between first and last.
If i is a Random Access Iterator, the function uses operator- to calculate this. Otherwise, the function uses repeatedly the increase or decrease operator (operator++ or operator--) until this distance is calculated.
Parameters
- first
- Iterator pointing to the initial element.
- second
- Iterator pointing to the final element. This must be reachable from first.
Return value
The number of increments or decrements needed to get from first to last.
Example
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// distance example
#include <iostream>
#include <iterator>
#include <list>
using namespace std;
int main () {
list<int> mylist;
for (int i=0; i<10; i++) mylist.push_back (i*10);
list<int>::iterator first = mylist.begin();
list<int>::iterator last = mylist.end();
cout << "The distance is: " << distance(first,last) << endl;
return 0;
}
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Output
Complexity
Constant for random access iterators.
Linear on the return value for other categories of iterators.
See also
| advance | Advance iterator (function template) |
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