struct tmp{
  bool charset[256];
..
  void include(char ch){ charset[ch] = true;	}
..
}

tcharset tcharset_union(tcharset a, tcharset b){
tcharset tmp;		
	
	for (unsigned int i=0;i<256;i++){	
		if (a.checkchar(i) || b.checkchar(i)){ 
			cout << "union" << endl;
			//tmp.include(char(i)); 	
		}
	}
	return tmp;
}