what do the words "noexcept, explicit, override" mean?

Question

#define LOVE noexcept

#define DEATH explicit

#define BEAUTY override

Answer 1

"noexcept" keyword denotes that a function won't propagate exceptions. If an exception is thrown, the exception won´t propagate to caller functions and program aborts in that function. Example:

void fun2() { throw 1; }

void fun1() noexcept {

  // if fun2 throws an exception
// program aborts here

  fun2();

}

"override" keyword in C++ is used in a similar way that @Override in java. It means that the funcion is overriding a virtual funcion. If there isn't a virtual funcion with that name it will generate an error. This is useful for avoiding typos. Example:

class A {

  virtual void foo()=0;

};

class B : A {

 // tried to override virtual foo function in base
class A. Typo fooo instead of foo will generate an error due to override keyword 

  void fooo() override {}

};

"explicit" keyword avoid object implicit initialization of classes with one parameter in order to avoid typos. Example:

class A {

public:

  int data;

  A(int i) { data = i; }

};

// Not allowed
A a ={ 3 };

// Must be
A a(3);

Answer 2

Ops ! sorry. This is the corrected example:

Explicit avoid object implicit initialization of classes with one parameter in order to avoid typos. Example:

class A {

public:

  int data;

  explicit A(int i) { data = i; }

};

// Not allowed

A a ={ 3 };

// Must be

A a(3);

Answer 3

thanks guy. your explain is very good but you didn't use from explicit keyword in your example.