[C++] Costruttori definiti fuori o dentro la classe

[vicio_93]

Salve Ragazzi, non capisco perchè ho sempre problemi quando definisco i costruttori fuori dal corpo classe:

//Persona.h
#ifndef PERSONA_H
#define PERSONA_H
#include "Data.h"
using namespace std;

class Persona{
public:
    Persona();
    Persona(string,string,Data);
    virtual void print()=0;
protected:
    string nome;
    string cognome;
    Data date;
};

class Studente : public Persona{
public:
    Studente ();
    Studente (string a, string b, Data c, string d);
    virtual void print();
    ~Studente();
protected:
    string CDL;
};

class Docente : public Persona{
public:
    Docente ();
    Docente (string a,string b,Data c,string d);
    virtual void print();
    ~Docente();
private:
    string Materia;
};

class StudenteSpecialista : public Studente{
public:
    StudenteSpecialista ();
    StudenteSpecialista (string,string,Data,string,string);
    virtual void print();
    ~StudenteSpecialista();
private:
    string LT;
};

#endif

//Persona.cpp
#include <iostream>
#include "Persona.h"
#include "Data.h"
using namespace std;


Persona::Persona(){
    nome="-";
    cognome="-";
}

Persona::Persona(string a, string b, Data c){
    nome=a;
    cognome=b;
    date=c;
}



Studente::Studente(){
    Persona();
    CDL="-";
}

Studente::Studente(string a,string b,Data c,string d){
    Persona(a,b,c);
    CDL=d;
}

void Studente::print(){
    cout<<nome<<endl<<cognome<<endl<<date<<endl<<CDL<<endl<<endl;
}

Docente::Docente(){
    Persona();
    Materia="-";
}

Docente::Docente(string a, string b, Data c, string d){
    Persona (a,b,c);
    Materia=d;
}

Studente::~Studente(){
    cout<<"Distruttore"<<endl;
}

Docente::~Docente(){
    cout<<"Distruttore"<<endl;
}

||=== Build: Debug in ese5 (compiler: GNU GCC Compiler) ===|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp||In constructor 'Studente::Studente()':|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp|21|error: cannot allocate an object of abstract type 'Persona'|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.h|6|note:   because the following virtual functions are pure within 'Persona':|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.h|10|note:     virtual void Persona::print()|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp||In constructor 'Studente::Studente(std::string, std::string, Data, std::string)':|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp|26|error: cannot allocate an object of abstract type 'Persona'|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.h|6|note:   since type 'Persona' has pure virtual functions|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp||In member function 'virtual void Studente::print()':|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp|31|error: cannot bind 'std::basic_ostream<char>::__ostream_type {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&'|
c:\program files\codeblocks\mingw\lib\gcc\mingw32\4.8.1\include\c++\ostream|602|error:   initializing argument 1 of 'std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits<char>; _Tp = Data]'|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp||In constructor 'Docente::Docente()':|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp|35|error: cannot allocate an object of abstract type 'Persona'|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.h|6|note:   since type 'Persona' has pure virtual functions|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp||In constructor 'Docente::Docente(std::string, std::string, Data, std::string)':|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.cpp|40|error: cannot allocate an object of abstract type 'Persona'|
C:\Users\Vinc\Desktop\Bill\Bill_ese_9\ese5\Persona.h|6|note:   since type 'Persona' has pure virtual functions|
||=== Build finished: 6 error(s), 0 warning(s) (0 minute(s), 1 second(s)) ===|

il main è un semplice file di prova..

//main.cpp
#include <iostream>
#include "Persona.h"
#include "Data.h"
using namespace std;

int main(){
    Studente l;
    Docente d;
}