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
);
Parameters
_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.
Return Value
The number of times that _First must be incremented until it equal _Last.
Remarks
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.
Example
// 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.
Requirements
Header: <iterator>
Namespace: std