DOCUMENT:Q156991  27-MAR-2002  [visualc]
TITLE   :INFO: STL Sample for the distance() Function
PRODUCT :Microsoft C Compiler
PROD/VER::4.2,5.0,6.0
OPER/SYS:
KEYWORDS:kbcode kbVC420 kbVC500 kbVC600 kbDSupport

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The information in this article applies to:

 - The Standard C++ Library, used with:
    - Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0 
    - Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0 
    - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
    - Microsoft Visual C++.NET (2002) 
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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
-----------

NOTE: The first line in the sample code section says:

   // Compile options needed: /GX

In VC++ .NET, /EHsc is set by default and is equivalent to /GX.

   ////////////////////////////////////////////////////////////////////// 
   // 
   // 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>

   #if _MSC_VER > 1020   // if VC++ version is > 4.2
      using namespace std;  // std c++ libs implemented in std
      #endif

   // disable warning C4244: possible loss of data,
   // okay to ignore

   #pragma warning(disable: 4244)

   #pragma warning (disable:4786)
   typedef vector<string, allocator<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

REFERENCES
==========

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

Additional query words: STL STLSample distance

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Keywords          : kbcode kbVC420 kbVC500 kbVC600 kbDSupport 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : :4.2,5.0,6.0
Issue type        : kbinfo

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