Microsoft KB Archive/156991

= How to use the distance STL function in Visual C++ =

Article ID: 156991

Article Last Modified on 8/11/2005

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Enterprise Edition

 Microsoft Visual C++ 6.0 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2002 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2003 Standard Edition</li></ul> </li></ul>

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This article was previously published under Q156991

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

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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 // // : distance.cpp // // Functions: // //   distance // // Written by Linda Koontz // of Microsoft Product Support Services, // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////


 * 1) include
 * 2) include
 * 3) include
 * 4) include

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

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


 * 1) pragma warning(disable: 4244)

typedef vector<string, allocator > VTRLIST;
 * 1) pragma warning (disable:4786)

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: <pre class="fixed_text">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

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