KB158207 - 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

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