Re: [Dev-C++] About member functions

[Jason H. <jas...@bt...>]

MessageI am not a pro for a start, but because of my background I tend =
to understand some of the concepts in Classes and Objects from a =
different perspective. My background being as a hardware engineer and =
using assembler (68000 mainly).

The section you are refering to is about pointers to member functions. =
Something that a class can do is provide a table of pointers to it's =
member functions in it's internal representation. There will still be =
only one instance of the member funstion, but each object will contain a =
pointer to that fuction. This is specifically needed in the case of =
virtual member functions where the caller doesn't necessarily know what =
class it is using. By saying that a particular pointer to the member is =
at such and such a position in an object then you can indirectly call =
the correct function for the object. Pointers to pointers are a useful =
form of indirection.

In essence what that paragraph is saying is that if you call method 5 =
(for example) of an object the compiler will know that it actualy refers =
to a particular function in a particular place in memory, or at least a =
pointer to that function in memory.

I will qoute from my edition (third) on the same page you quote:
"C++ offers a facility for indirectly referring to member of a class. A =
pointer to a member is a *value* that identifies a member of a class. =
You can think of it as the position of the member in an object of the =
class, but of course an implementation takes into account the =
differences between data members, virtual functions, non-virtual =
functions, etc."

Does that seem reasonable to you? It seems that we are looking at the =
same paragraphs and getting two totally different answers from it.

Jason.
  ----- Original Message -----=20
  From: Ioannis Vranos=20
  To: Dev-C++=20
  Sent: Wednesday, October 31, 2001 8:11 PM
  Subject: [Dev-C++] About member functions


  This subject has been discussed on th e past, but now new evidence =
came up. :)


  In "The C++ Programming Language" Special Edition on page 419 it says =
that each object has its own member function as i was claiming in the =
beginning.


  It says many things but lets concentrate at the end of that page:

  "Just like ordinary pointers to functions, pointers to member =
functions are used when we need to refer to a function without having to =
know its name. However, a pointer to member isn't a pointer to a piece =
of memory the way a pointer to a variable or a pointer to a function is. =
It is more like an offfset into a structure or an index into an array. =
When a pointer to member is combined with a pointer to an object of the =
right type, it yields something that identifies a particular member of a =
particular object".


  i think we were discussing it with Jason Hardman. Jason if you see it, =
please tell me your opinion (since you seem you are a pro).


  Ioannis

  * Ioannis Vranos
  * Programming pages: http://www.noicys.f2s.com
  * Alternative URL: http://run.to/noicys