🚀 go-pugleaf

G'day,

Bruce Lai wrote:
> 
>     Hello great programmers, I got a question here. Please take a look
> at the code below.
> 
>     class derived : public base {
>         public:
>             derived()  :  base() {}  //What the hell does this line of
> code do?
>     }

Because derived is a specialisation of base then all of the properties
of an object of type base are necessarily properties of an object of
type derived.  This constructor for a derived object causes the base
bits to be properly constructed by including the base constructor in the
initialisation list.

> 
> I see this kind of declaration in an example of OWL programming and in
> the case derived is TDrawApp and base is TApplication.
> 
> Well, something out of the content but I saw this in my C++ book and I
> can't make clear of them:
> 

Favoured by pathological teachers as exam questions and more than likely
the last time you will see such evil (although I must admit to writing
something similarly nasty in C to adapt some legacy code).

The trick is to start at the symbol and work outwards keeping track of
precedences and associativity.  Here goes <deep breath>

>     int *(*(*ifunct_ptr)(int))[5];

A declaration of ifunct_ptr which is a pointer to a function that takes
one int argument and returns a pointer to an array of 5 pointers to int

>     float (*(*ffunct_ptr)(int,int))(float);

A declaration of ffunct_ptr which is a pointer to a function that takes
2 int arguments and  returns a pointer to a function that takes one
float argument and returns a float

>     typedef double (*(*(*dfunct_ptr)())[5])();

A type definition for dfunct_ptr which is defined as a pointer to a
function that takes no arguments and returns a pointer to an array of 5
pointers to functions that take no arguments and return doubles

>     (*(*funtion_ary_ptrs())[5])();

A statement comprising a call to function_ary_ptrs, then dereferencing
the return value (which will be a pointer to an array of pointers to
functions that take no argument) and calling the sixth element
(function) in that array.

>     int func() const;

This is a declaration of a member function that takes no argument,
returns an int and does not change the object of which the method is a
property.

Cheers,
Gryff