This topic has not yet been rated - Rate this topic

# distance

Visual Studio 2013

Determines the number of increments between the positions addressed by two iterators.

```template<class InputIterator>
typename iterator_traits<InputIterator>::difference_type
distance(
InputIterator _First,
InputIterator _Last
);
```
_First

The first iterator whose distance from the second is to be determined.

_Last

The second iterator whose distance from the first is to be determined.

The number of times that _First must be incremented until it equal _Last.

The distance function has constant complexity when InputIterator satisfies the requirements for a random-access iterator; otherwise, it has linear complexity and so is potentially expensive.

```// iterator_distance.cpp
// compile with: /EHsc
#include <iterator>
#include <list>
#include <iostream>

int main( )
{
using namespace std;
int i;

list<int> L;
for ( i = -1 ; i < 9 ; ++i )
{
L.push_back ( 2 * i );
}
list <int>::iterator L_Iter, LPOS = L.begin ( );

cout << "The list L is: ( ";
for ( L_Iter = L.begin( ) ; L_Iter != L.end( ); L_Iter++ )
cout << *L_Iter << " ";
cout << ")." << endl;

cout << "The iterator LPOS initially points to the first element: "
<< *LPOS << "." << endl;

advance ( LPOS , 7 );
cout << "LPOS is advanced 7 steps forward to point "
<< " to the eighth element: "
<< *LPOS << "." << endl;

list<int>::difference_type Ldiff ;
Ldiff = distance ( L.begin ( ) , LPOS );
cout << "The distance from L.begin( ) to LPOS is: "
<< Ldiff << "." << endl;
}
```
```The list L is: ( -2 0 2 4 6 8 10 12 14 16 ).
The iterator LPOS initially points to the first element: -2.
LPOS is advanced 7 steps forward to point  to the eighth element: 12.
The distance from L.begin( ) to LPOS is: 7.```