distance (STL Sample)

The sample code below illustrates how to use the distance STL function in Visual C++.

Required Header:
<iterator>

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

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

Description:
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.

Sample Code:

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// <filename> :  distance.cpp
//
// Functions:
//
//    distance()
//////////////////////////////////////////////////////////////////////

#include <iostream>
#include <vector>
#include <iterator>
#include <string>

using namespace std;


#pragma warning (disable:4786)
typedef vector<string > VTRLIST;

void 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;
}

 

Program Output is:

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