How to use the string::operator+ STL function in Visual C++ (158207)


The information in this article applies to:

  • The Standard C++ Library, when used with:
    • Microsoft Visual C++, 32-bit Enterprise Edition 4.2
    • Microsoft Visual C++, 32-bit Enterprise Edition 5.0
    • Microsoft Visual C++, 32-bit Enterprise Edition 6.0
    • Microsoft Visual C++, 32-bit Professional Edition 4.2
    • Microsoft Visual C++, 32-bit Professional Edition 5.0
    • Microsoft Visual C++, 32-bit Professional Edition 6.0
    • Microsoft Visual C++, 32-bit Learning Edition 6.0
    • Microsoft Visual C++ 2005 Express Edition
    • Microsoft Visual C++ .NET (2003)
    • Microsoft Visual C++ .NET (2002)
This article was previously published under Q158207
Note Microsoft Visual C++ .NET 2002 and Microsoft Visual C++ .NET 2003 support both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model. The information in this article applies only to unmanaged Visual C++ code. Microsoft Visual C++ 2005 supports both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model.

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
       basic_string<_E, _TYPE, _A>
       operator+(const basic_string<_E, _TYPE, _A>& LString,
                 const _E *RCharArray);

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

   Function 3:
       template<class _E, class _TYPE, class _A> inline
       basic_string<_E, _TYPE, _A>
       operator+(const basic_string<_E, _TYPE, _A>& LString,
                 const _E RChar);

   Function 4:
       template<class _E, class _TYPE, class _A> inline
       basic_string<_E, _TYPE, _A>
       operator+(const _E LChar,
                 const basic_string<_E, _TYPE, _A>& RString);

   Function 5:
       template<class _E, class _TYPE, class _A> inline
       basic_string<_E, _TYPE, _A>
       operator+(const basic_string<_E, _TYPE, _A>& LString,
                 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 five versions of the string::operator+ function. Two functions are used to concatenate a null-terminated character array and a basic_string. Two functions are used to concatenate a character and a basic_string. The last function is used to concatenate two basic_string variables.

Sample code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: /GX
// 
// StringPlus.cpp : Illustrates how to use the operator+ to concatenate
//                  a null-terminated character array and a basic_string,
//                  how to concatenate a character and a basic_string,
//                  and how to concatenate two basic_string variables.
// 
// Functions:
// 
//    operator+ : Concatenates a null-terminated character array and
//                a basic_string.
//    operator+ : Concatenates a character array and a basic_string.
//    operator+ : Concatenates two basic_string variables.
// 
// Written by Derek Jamison
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
////////////////////////////////////////////////////////////////////// 

// The debugger can't handle symbols more than 255 characters long.
// STL often creates symbols longer than that.
// When symbols are longer than 255 characters, the warning is disabled.

#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 main()

{

   string result;
   string S1="ABC";
   string S2="DEF";
   char CP1[]="GHI";
   char C='J';

   cout << "S1 is " << S1 << endl;
   cout << "S2 is " << S2 << endl;
   cout << "CP1 is " << CP1 << endl;
   cout << "C is " << C << endl;

   result=S1+CP1;                           // Function 1  (ABCGHI)
   cout << "S1+CP1 is " << result << endl;

   result=CP1+S1;                           // Function 2  (GHIABC)
   cout << "CP1+S1 is " << result << endl;

   result=S1+S2;                            // Function 3  (ABCDEF)
   cout << "S1+S2 is " << result << endl;

   result=S1+C;                             // Function 4  (ABCJ)
   cout << "S1+C is " << result << endl;

   result=C+S1;                             // Function 5  (JABC)
   cout << "C+S1 is " << result << endl;

}
Program Output is: 
S1 is ABC
S2 is DEF
CP1 is GHI
C is J
S1+CP1 is ABCGHI
CP1+S1 is GHIABC
S1+S2 is ABCDEF
S1+C is ABCJ
C+S1 is JABC

REFERENCES

For more information about string::operator+, visit the following Microsoft Developer Network (MSDN) Web site:

http://msdn.microsoft.com/library/en-us/vcstdlib/html/vcsampsamplestringccoperatorpstlsample.asp?frame=true

Modification Type:MajorLast Reviewed:1/9/2006
Keywords:kbhowto kbcode kbinfo KB158207 kbAudDeveloper
©2004 Microsoft Corporation. All rights reserved.