mif02-prog-avancee-2021

• TP1 Constructeurs, destructeurs, temporaires et conversions.
• TP2 Capsule RAII, déplacement, affectation des classes dérivées, upcast et downcast, écriture d'une classe String.
• TP3 Objets fonctions, Polymorphisme.
• TP4 Polymorphisme.
• TP5 Template.
• TP6 Template, itérateurs et STL.
• TP7 Template, itérateurs, Inserteurs, STL, déplacement.
• TP8 Métaprogrammation, Const_cast.

Useful commands:

• g++ -fno-elide-constructors -Wall -std=c++11 -ggdb -o exec CapsuleRAII.cpp
  The -ggdb option of g++ for debugging with Valgrind. With that option Valgrind will show the exact lines where a leak happened.
• valgrind --tool=memcheck --leak-check=full --track-origins=yes --verbose ./exec

Bottom Line:

virtual

makes a member function and its class POLYMORPHIC (virtual member functions are called METHODS)

=> POLYMORPHISM when a polymorphic function is called via pointer or reference of base class type, but that is actually pointing to one of its derived classes it will call the derived classes version, and not the one of the base class.

• Virtual functions should be accessed using pointer or reference of base class type to achieve run time polymorphism.
• The prototype of virtual functions should be the same in the base as well as derived class.
• It is not mandatory for the derived class to override (or re-define the virtual function), in that case, the base class version of the function is used.
• A class may have virtual destructor but it cannot have a virtual constructor.

class Enemy {
public:
	virtual void attack() {
		std::cout << "Enemy attacks!" << std::endl;
	}
};

class Monster : public Enemy {
public:
	void attack() {
		std::cout << "Monster attacks!" << std::endl;
	}
};

int main() {
	Monster m;
	
	Enemy* ptrE = &m;
	ptrE->attack(); // Prints "Monster attacks!"
	
	Enemy& refE = m;
	refE.attack(); // Prints "Monster attacks!"
	
	Enemy e = m;
	e.attack(); // Prints "Enemy attacks!";
	
	return 0;
}

---

=0

makes the method PURE VIRTUAL Declared but without definition, so MUST be defined in the derived classes.

=> A class that has a pure virtual method is called ABSTRACT, and cannot be directly instantiated !

• Must be overriden in the derived classes.
• If we do not override the pure virtual function in derived class, then derived class also becomes abstract class.
• We can have pointers and references whose static type is an abstract class type.

---

override

explicitly indicating that the function is a redefinition. Is used to avoid problems with masking base class's functions.

---

using

Is used to avoid problems with masking base class's functions.

Masking / Dominance : Inheritance relies on a basic mechanism called Masking or Dominance, which states that a definition of a derived class D of B corresponds to introduction of a new scope that dominates over the one of B. Thus, an identifier F in the scope of D, hides all the same identifiers inherited from B. Masking is based only on the identifiers and not the type !

=> Brings ALL Base::f out of the hidden scope

class B {
public:
	void f(int) {
		std::cout << "void B::f(int)" << std::endl;
	}
	void f(double) {
		std::cout << "void B::f(double)" << std::endl;
	}
};

class D : public B {
public:
	// here f is an overload of f, and not the redefinition
	int f(int, int) {
		std::cout << "int D::f(int, int)" << std::endl;
	}
	using B::f; // brings ALL B::f out of the hidden scope
};

int main() {
	D d; 
	d.f(3);
	// OK with 'using'
	// Otherwise ERROR: no matching function for call to 'D::f(int)'
	
	return 0;
}

---

explicit

Prohibits an implicit conversion when a member function prefixed with explicit is called.

---

=default

Explicitly indicates that the member function's declaration postfixed with =default, should use the implementation proposed by the compiler by default.

• Can be used only with special member functions

struct LaClasse {
	LaClasse() =default; //C++11
	~LaClasse() =default; //C++11
	// … blablacode …
};

---

=delete

Explicitly indicates that the implementation proposed by the compiler by default of the member function declared with =delete, should be removed.

class A {
private:
	int n;
public:
	A(int x) : n(x) {}
	
	A(double) =delete;
	
	// Delete the copy constructor
	A(const A&) =delete;
	
	// Delete the copy assignment operator
	A& operator=(const A&) =delete;
};

int main() {
    A a1(1), a2(2), a3(3);
    
    // Error, disabled
    A a4(3.14);
     
    // Error, the usage of the copy
    // assignment operator is disabled
    a1 = a2;
     
    // Error, the usage of the
    // copy constructor is disabled
    a3 = A(a2);
    return 0;
}

---

final

=> A final class cannot be derived.