typecast.cpp

// #define DEBUG_SHOW_DUMP_CHALLENGE_2
#pragma GCC diagnostic ignored "-Wunused-variable"

// Prevent big size of .class file
#ifndef DEBUG_SHOW_DUMP_CHALLENGE_2

#include <iostream>
#include <typeinfo>
using namespace std;

class D
{
  int i;
public:
  D() : i(0) { cout << "D::D()" << endl; }
  D(int _i) : i(_i) { cout << "D::D(int)" << endl; }
  ~D() { cout << "D::~D()" << endl; }
  void set(int _i) { i = _i;}
  int get() const { return i; }
};

class E : public D {
  double d;
public:
  E() : d(0.0) { cout << "E::E()" << endl; }
  E(double _d) : d(_d) { cout << "E::E(double)" << endl; }
  ~E() { cout << "E::~E()" << endl; }
  void set(double _d) { d = _d;}
  double get() const { return d; }
};

// Const cast
void challenge0() {
  const D* d = new D(1);
  // d->set(2);
  D* d1 = const_cast<D*>(d);
  d1->set(2);
  // *i = 'T';
  cout << d1->get() << ", " << d->get() << endl;
  delete d;
}
// Static_cast
void challenge1() {
  // basic types
  int ii = 10;
  double test = 10;
  double dd = static_cast<double>(ii);
  float tmp_f = static_cast<float>(ii);
  cout << typeid(ii).name() << "["<< ii << "], "
       << typeid(dd).name() << "["<< dd << "], "
       << typeid(tmp_f).name() << "["<< tmp_f << "], " << test << endl;

  // User types
  // Upcast
  E* e1 = new E(0.1);
  D* d1 = static_cast<D*>(e1);
  cout << e1->get() << ", " << d1->get() << endl;
  delete e1;
  // downcast
  // undefined behavior
  D* d2 = new D(2);
  E* e2 = static_cast<E*>(d2);
  cout << d2->get() << ", " << e2->get() << endl;
  delete d2;
}

class nonVirtual {
public:
  nonVirtual() { cout << "nonVirtual::nonVirtual()" << endl; }
  ~nonVirtual() { cout << "nonVirtual::~nonVirtual()" << endl; }
};

class AnonVirtual : public nonVirtual {
public:
  AnonVirtual() { cout << "AnonVirtual::AnonVirtual()" << endl; }
  ~AnonVirtual() { cout << "AnonVirtual::~AnonVirtual()" << endl; }
};
class BnonVirtual : public AnonVirtual
{
public:
  BnonVirtual() { cout << "BnonVirtual::BnonVirtual()" << endl; }
  ~BnonVirtual() { cout << "BnonVirtual::~BnonVirtual()" << endl; }
};
#endif
/* end define */

class Base {
public:
  Base() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "Base::Base()" << endl;
    #endif
  }
  virtual ~Base() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "Base::~Base()" << endl;
    #endif
  }
  virtual void print() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "Base::print()" << endl;
    #endif
  }
};

class A : public Base {
public:
  A() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "A::A()" << endl;
    #endif
  }
  virtual ~A() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "A::~A()" << endl;
    #endif
  }
  virtual void print() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "A::print()" << endl;
    #endif
  }
};

class B : public A {
public:
  B() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "B::B()" << endl;
    #endif
  }
  virtual ~B() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "B::~B()" << endl;
    #endif
  }
  virtual void print() {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
      cout << "B::print()" << endl;
    #endif
  }
};

void challenge2() {
  // Use non polymorphic classes
  // source type is not polymorphic - compile error
  // nonVirtual* nv = new nonVirtual();
  // BnonVirtual* bnv = dynamic_cast<BnonVirtual*>(nv);

  // Use polymorphic
  // Upcasting(from derived class to base)
  B* b = new B;
  Base* tmp_base = new Base;
  if (Base* base = dynamic_cast<Base*>(b)) {
    base->print();
  } else {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
    cout << "base is null" << endl;
    #endif
  }
  // Crosscasting
  if (A* a = dynamic_cast<A*>(b)) {
    a->print();
  } else {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
    cout << "a is null" << endl;
    #endif
  }
  // Downcasting
  // tmp_b == null
  if (B* tmp_b = dynamic_cast<B*>(tmp_base)) {
    tmp_b->print();
  } else {
    #ifndef DEBUG_SHOW_DUMP_CHALLENGE_2
    cout << "tmp_b is null" << endl;
    #endif
  }
  delete b;
}

typedef void(B::*pmemory)();
typedef void(Base::*pmemory_polymoph)();

// Pointer to member
void challenge3() {
  B* b = new B;
  pmemory p = &B::print;
  b->print(); // direct call
  (b->*p)();
  delete b;
  // Polymorph classes
  Base* base = new B;
  pmemory_polymoph pp = &Base::print;
  base->print();
  (base->*pp)();
  delete base;
}

int main() {
  // challenge0();
  // challenge1();
  // challenge2();
  challenge3();
  return 0;
}