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);
				

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

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

Note 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
// 
// StringLessEqual.cpp : Illustrates how to use the operator<= to compare
//                       a basic_string variable to a null-terminated
//                       string.
// 
// Functions:
// 
//    operator<=   Returns true if the second parameter is not less
//                 than the first.
// 
// Written by Derek Jamison
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
///////////////////////////////////////////////////////////////////////// 

#pragma warning(disable:4786)

#include <string>
#include <iostream>
using namespace std;

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

void trueFalse(int x)

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

void main()
{
   string S1="DEF";
   char CP1[]="ABC";
   char CP2[]="DEF";
   char CP3[]="DEFG";
   char CP4[]="def";

   cout << "S1 is " << S1 << endl;
   cout << "CP1 is " << CP1 << endl;
   cout << "CP2 is " << CP2 << endl;
   cout << "CP3 is " << CP3 << endl;
   cout << "CP4 is " << CP4 << 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);  // True   (calls function 2)

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

   cout << "CP4<=S1 returned ";
   trueFalse(CP4<=S1);  // False   (calls function 2)

}
				

Program Output is:

S1 is DEF
CP1 is ABC
CP2 is DEF
CP3 is DEFG
CP4 is def
S1<=CP1 returned False
S1<=CP2 returned True
S1<=CP3 returned True
CP1<=S1 returned True
CP2<=S1 returned True
CP4<=S1 returned False