Класс String, перегрузка сложения и вычитания

#ifndef STRING_H
#define STRING_H
 
class cString
{
private:
    char* symbol;
    int length;
 
public:
    cString ();
    cString (const char*);
    ~cString ();
    void Set();
    void Get ();
    bool operator==(const cString&);
    bool operator<(const cString&);
    bool operator>(const cString&);
    cString operator+(cString&);
    //char operator-(cString&);
};
#endif

# include <iostream>
# include "STRING.h"
 
using namespace std;
 
# include <iostream>
 
using namespace std;
 
cString::cString()
{
    length = 0;
    strcpy(symbol,"");
}
 
cString::cString(const char* str)
{
    length = strlen(str);
    symbol = new char [length+1];
    strcpy (symbol,str);
}
cString::~cString()
{
    delete [] symbol;
}
 
void cString::Get()
{
    cout<<symbol;
}
bool cString::operator==(const cString & str)
{
    return strcmp(symbol,str.symbol)==0;
}
bool cString::operator<(const cString & str)
{
    return strcmp(symbol,str.symbol)<0;
}
bool cString::operator>(const cString & str)
{
        return strcmp(symbol,str.symbol)>0;
}
 
cString cString::operator+(cString & str)
{
    size_t new_length  = length+str.length;
    char *new_symbol = new char [new_length+1];
    strcpy(new_symbol,symbol);
    strcpy(new_symbol+length,str.symbol);
    symbol = new_symbol;
    length = new_length;
    delete [] new_symbol;
 
    return *this;
}

# include <iostream>
# include "STRING.h"
 
using namespace std;
 
int main()
{
    cString string("Hello");
    cString string1("Hello!");
        string+string1;
 
    return 0;
}

cString cString::operator+(cString & str)
{
    size_t new_length  = length+str.length;
    char *new_symbol = new char [new_length+1];
    strcpy(new_symbol,symbol);
    strcat(new_symbol,str.symbol);
    cString tmp(new_symbol);
    delete[] new_symbol;
    return tmp;
}

cString s = string + string1;

cString::cString()
{
    length = 0;
    symbol = NULL;
}