STL Sample for the distance() Function

• The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Edition, version 4.2

SUMMARY

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

MORE INFORMATION

Required Header

   <iterator>

Prototype

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

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.

The Help file in Visual C++ 4.2 incorrectly states that this function takes three parameters and returns nothing.

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

Sample Code

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// <filename> :  distance.cpp
//
// Functions:
//
//    distance()
//
// Written by Linda Koontz
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////

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

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

REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.