Newby: VC6 errors

Hello,

I am trying to understand why this string concatenation is not
working. Could someone shed some light on this and tell me what I'm
doing wrong?

TIA..

---Errors:---
ParseLineDemo.cpp
C:\ParseLineDemo\ParseLineDemo.cpp(245) : error C2784: 'class
std::reverse_iterator<_RI,_Ty,_Rt,_Pt,_D> __cdecl std::operator +
(_D,const class std::reverse_iterator<_RI,_Ty,_Rt,_Pt,_D> &)' : could
not deduce template argument for '' from 'class
std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >'

C:\ParseLineDemo\ParseLineDemo.cpp(245) : error C2676: binary '+' :
'class std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >' does not define this operator or a conversion
to a type acceptable to the predefined operator

---ParseLineDemo.h---
#include "stdafx.h"
#include <string.h>
#include <vector>
using namespace std;

union POD //Plain Ordinary Data
{
    int i;
    float f;
};

class DataSegment
{
    public:
        DataSegment(){}; //default constructor
        ~DataSegment();
        void setHeader(char dH[4]);
        void Push(POD p);
        string toString();
        void Clear(); //empty out the object

    private:
        char dataHeader[4]; //the name of the segment e.g. S[ or D[
        vector<POD> components;

};

---ParseLineDemo.cpp---
....

string DataSegment::toString()
{
    string szOutput;
    int i;
    szOutput = dataHeader;
    szOutput = szOutput + "[" //error occurs here
    for (i = 0; i < components.size(); i++)
    {
        szOutput = szOutput + components[i].i + ",";
    }

    //remove last comma and add closing bracket
    szOutput = szOutput.substr(0, szOutput.length() - 1) + "]";

    return szOutput;
}

....