Microsoft KB Archive/157670

= How to use the pair logical operator Standard Template Library (STL) functions in Visual C++ =

Article ID: 157670

Article Last Modified on 7/15/2005

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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 Q157670

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Note Microsoft Visual C++ NET (2002) supported both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model. The information in this article applies to unmanaged Visual C++ code only.

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SUMMARY
The sample code below illustrates how to use the pair logical operator STL functions in Visual C++.

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Prototype
It is interesting to note that only the < and == operators are necessary in order to define all of the logical operators. template<class _T1, class _T2> inline

bool operator==(const pair<_T1, _T2>& _X,        const pair<_T1, _T2>& _Y) {return (_X.first == _Y.first && _X.second == _Y.second); }

template<class _T1, class _T2> inline

bool operator<(const pair<_T1, _T2>& _X,        const pair<_T1, _T2>& _Y) {return (_X.first < _Y.first ||        !(_Y.first < _X.first) && _X.second < _Y.second); } Note The class/parameter names in the prototype may not match the version in the header file. Some have been modified to improve readability.

Description
The functions are described in the comments section of the sample.

Sample code
///////////////////////////// // Compile options needed: none // // paircomp.cpp : Illustrates several comparison //               operators used to compare two //               pair objects. // // Functions: // //   operator== - returns true if two pair objects are identical. // //   operator!= - returns true if two pair objects are not identical. // //   operator<  - returns true for (A < B) if pair object A is less //                than pair object B. // //   operator<= - returns true for (A <= B) if pair object A is less //                than or equal to pair object B. // //   operator>  - returns true for (A > B) if pair object A is greater //                than pair object B. // //   operator>= - returns true for (A >= B) if pair object A is greater //                than or equal to pair object B. // // Written by Mark Hagen // of Microsoft Technical Support // Copyright (c) 1996 Microsoft Corporation. // All rights reserved. /////////////////////////////


 * 1) include
 * 2) include

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

/* STL pair data type containing int and float */

typedef struct pair<int, float> PAIR_IF;

void main(void)

{ PAIR_IF A(10,3.14); PAIR_IF B(18,3.14); PAIR_IF C(10,6.28); PAIR_IF D(10,3.14);

/* show pair values */

cout << "A = ( " << A.first << ", " << A.second << " )" << endl; cout << "B = ( " << B.first << ", " << B.second << " )" << endl; cout << "C = ( " << C.first << ", " << C.second << " )" << endl; cout << "D = ( " << D.first << ", " << D.second << " )" << endl;

/* operator== */

if (A==D)

cout << "A and D are equal" << endl;

else

cout << "A and D are not equal" << endl;

/* operator!= */

if (B!=C)

cout << "B and C are not equivalent" << endl;

else

cout << "B and C are equivalent" << endl;

/* operator> */

if (A>C)

cout << "A is greater than C" << endl;

else

cout << "A is not greater than C" << endl;

/* operator>= */

if (A>=C)

cout << "A is greater than or equal to C" << endl;

else

cout << "A is not greater than or equal to C" << endl;

/* operator< */

if (C<D)

cout << "C is less than D" << endl;

else

cout << "C is not less than D" << endl;

/* operator<= */

if (C<D)

cout << "C is less than or equal to D" << endl;

else

cout << "C is not less than or equal to D" << endl;

} Program Output is: <pre class="fixed_text">A = ( 10, 3.14 ) B = ( 18, 3.14 ) C = ( 10, 6.28 ) D = ( 10, 3.14 ) A and D are equal B and C are not equivalent A is not greater than C A is not greater than or equal to C C is not less than D C is not less than or equal to D

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