distance (STL Samples)

Illustrates how to use the distance Standard Template Library (STL) function in Visual C++.

template<class Init, class Dist>
   Dist distance(
      InIt first,
      InIt last,
      Dist& n
   );

Remarks

Notes

The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

This function returns the distance between two iterators by determining how many times the first iterator would need to be incremented until it was equal to the last iterator.

Example

// distance.cpp
// compile with: /EHsc

#pragma warning (disable:4786)
#include <iostream>
#include <vector>
#include <iterator>
#include <string>

using namespace std;

typedef vector<string > VTRLIST;

int main() {
    VTRLIST Vector;
    VTRLIST::iterator iVector;
    VTRLIST::difference_type dTheDiff;

    Vector.push_back("A1");
    Vector.push_back("B2");
    Vector.push_back("C3");
    Vector.push_back("D4");
    Vector.push_back("E5");
    Vector.push_back("F6");
    Vector.push_back("G7");

    // Print out the list
    iVector=Vector.begin();
    cout << "The list is: ";
    for (int i = 0; i < 7 ; i++, iVector++)
        cout << *iVector  << "  ";

    // Initialize the iterator the first element"
    iVector=Vector.begin();
    cout << "\n\nAdvance to the 3rd element." << endl;
    advance( iVector, 2);
    cout << "The element is " << *iVector << endl;
    dTheDiff = distance( Vector.begin(), iVector);
    cout << "The distance from the beginning is " << dTheDiff << endl;

    cout << "Calculate it in reverse order " << endl;
    dTheDiff = distance( iVector, Vector.begin());
    cout << "The distance is " << dTheDiff << endl;

    cout << "\nUse distance() to count from the 3rd element to the end."
         << endl;
    dTheDiff = distance( iVector, Vector.end());

    // Note that end() returns one past the end of the sequence
    cout << "The distance is " << dTheDiff << endl;

    cout <<"\nUse distance() to count the total length." << endl;
    dTheDiff = distance( Vector.begin(), Vector.end() );
    cout << "The total distance is " << dTheDiff << endl;
}

Output

The list is: A1  B2  C3  D4  E5  F6  G7  

Advance to the 3rd element.
The element is C3
The distance from the beginning is 2
Calculate it in reverse order 
The distance is -2

Use distance() to count from the 3rd element to the end.
The distance is 5

Use distance() to count the total length.
The total distance is 7

Requirements

Header: <iterator>

See Also

Concepts

Standard Template Library Samples