STL Sample for the string::operator!= Function

The information in this article applies to:

• 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 string::operator!= STL function in Visual C++.

MORE INFORMATION

Required Header

   <string>

Prototype

   Function 1:
       template<class _E, class _TYPE, class _A> inline
       bool operator!=(const basic_string<_E, _TYPE, _A>& LString,
                       const _E *RCharArray);

   Function 2:
       template<class _E, class _TYPE, class _A> inline
       bool operator!=(const _E *LCharArray,
                       const basic_string<_E, _TYPE, _A>& RString);

Description

There are two versions of the string::operator!= function. Both versions are used to compare a null-terminated character array against a basic_string. They perform this operation by negating the result of (LString==RCharArray) or (LCharArray==RString). For more information on this comparison, please see the string::operator== function.

Notice that this operator does not work with NULL pointer for the character array. You will need to make sure that the character array is not NULL before you pass it to the operator.

Sample Code

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// StringNotEqual.cpp : Illustrates how to use the operator!= to test for
//                      non-equality of a basic_string variable and a
//                      null-terminated string.
//
// Functions:
//
//    operator!=   Returns true if the basic_string and the null-
//                 terminated string are not equal.
//
// Written by Derek Jamison
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////

#include <string>
#include <iostream>

void trueFalse(int x)

  cout << (x? "True": "False") << endl;

void main()

   string S1="ABC";
   char CP1[]="ABC";
   char CP2[]="DEF";
   char CP3[]="abc";

   cout << "S1 is " << S1 << endl;
   cout << "CP1 is " << CP1 << endl;
   cout << "CP2 is " << CP2 << endl;
   cout << "CP3 is " << CP3 << endl;

   cout << "S1!=CP1 returned ";
   trueFalse(S1!=CP1);  // False  (calls function 1)

   cout << "S1!=CP2 returned ";
   trueFalse(S1!=CP2);  // True   (calls function 1)

   cout << "S1!=CP3 returned ";
   trueFalse(S1!=CP3);  // True   (calls function 1)

   cout << "CP1!=S1 returned ";
   trueFalse(CP1!=S1);  // False  (calls function 2)

   cout << "CP2!=S1 returned ";
   trueFalse(CP2!=S1);  // True   (calls function 2)

   cout << "CP3!=S1 returned ";
   trueFalse(CP3!=S1);  // True   (calls function 2)
}

S1 is ABC CP1 is ABC CP2 is DEF CP3 is abc S1!=CP1 returned False S1!=CP2 returned True S1!=CP3 returned True CP1!=S1 returned False CP2!=S1 returned True CP3!=S1 returned True

REFERENCES

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