error: aggregate '' has incomplete type and cannot be defined.

Help!!! I´m working in a project and when I try to compile I got plenty errors... one of them if error: aggregate 'Parser parser' has incomplete type and cannot be defined.
The code where appears it is:

insert

Code:

class Parser;

#ifndef CFUNCION_H
#define CFUNCION_H

#include "Parser.h"
#include "CTermino.hpp"

//using namespace std;

class CFuncion: public CTermino {

//.... stuff

  bool operator==( CTermino *ter2 )
    //Sobrecarga del operador "==" que define una relación entre dos términos,
    //la relación de IGUALDAD. Informalmente, dos terminos son IGUALES cuando cada uno de los simbolos
    //que componen al término los son. Es decir, viéndo los términos como cadenas, las cadenas deberán ser
    //exactamente iguales
    {
        bool ig = true;
         Parser parser;
        if (!ter2->perteneceVariable(ter2) && !parser.esConstante(ter2)){
//Se que son funciones
//Deberia castear a funcion para poder usar los metodos propios?
                list<CTermino> * listTer1 = this->getListaParametros();
                list<CTermino> * listTer2 = ter2->getListaParametros();
                list<CTermino>::iterator it1 = listTer1->begin();
                list<CTermino>::iterator it2 = listTer2->begin();

                while ( ((it1 != listTer1->end()) || (it2 != listTer2->end())) && ig)
                {
                //Si tienen distinta cantidad de parametros, es decir, alguno llego al final antes que el otro
                if (((it1 == listTer1->end()) && (it2 != listTer2->end())) ||
                    ((it1 != listTer1->end()) && (it2 == listTer2->end())))
                    ig = false;
                else
                    ig = (*it1) == (*it2); //que pasa aca?? :S
                //Aca estoy pidiendo equivalencia entre el componente de los terminos...

                it1++; it2++;
                }
                delete listTer1;
                delete listTer2;
            }
        else
            ig=false;

            return ig;
    }

Could someone help me??? What is the reason of that error?? What should I do to correct it??
Thanks in advance!!!

I don't suppose that Parser.h includes CFuncion.h?

Yes... It´s something like a 'cross reference'... Parser needs CFuncion and then I want to use a method of Parser inside CFuncion... is that posible to do?

That's what is causing your problem. If you move the code to a .cpp file instead of putting everything in the header, that will put you on the right track. You can then get rid of the #include Parser.h from this header file.

The general rule is: Never let 2 header files include each other.

Thanks a lot!!!! That work out!!! I appreciate your help!!!! Thank you very much!!!