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lovecreatesbeauty
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 Posted: Fri Apr 29, 2005 3:46 am Post subject: Predefined class member functions and inheritance |
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Predefined class member functions and inheritance
How many member functions on earth can be provided (predefined) by
standard-compliant compilers?
Scott Meyers says that there are 6: (1)default constructor, (2)copy
constructor, (3)destructor, (4)assignment operator, (5)address-of
operator (non-const), (6)address-of operator (const), in `Effective
C++, 2nd` item 45.
Bjarne Stroustrup mentioned one more: operator, (i.e. comma operator)
in `The C++ programming Language, special edition` section 11.2.2.
Derived classes won't inherit these member functions provided
(predefine) by compilers from father classes, right?
Thank you
lovecreatesbeauty
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Ron Natalie
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| Posted: Fri Apr 29, 2005 12:44 pm Post subject: Re: Predefined class member functions and inheritance |
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lovecreatesbeauty wrote:
| Quote: | Scott Meyers says that there are 6: (1)default constructor, (2)copy
constructor, (3)destructor, (4)assignment operator, (5)address-of
operator (non-const), (6)address-of operator (const), in `Effective
C++, 2nd` item 45.
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If Scott actually says what you say, he's wrong. The only FUNCTIONS
provided are the default constructor, the copy constructor, the
destructor, and the copy-assignment operator.
It is possible to override other operators for the class (such as
ampersand and comma) but these aren't "predefined member functions"
but intrinsic operators that can be replaced.
| Quote: | Derived classes won't inherit these member functions provided
(predefine) by compilers from father classes, right?
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Constructors and destructors aren't "inheritted". The copy-assignment
operator (as you noted) is covered up with either the compiler generated
one or a user defined one in the derived class.
As for the operators& and ,. There is no intrisicly operator function
generated when these are not-defined. If you don't define one, then the
default behavior occurs. If you define one in a base class and don't
overload it, the derived class if it can be converted to the base, will
be:
struct A {
A* operator&() { return 0; }
} a;
struct B : A { } b;
cout << &b;
will call A::operator&();
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Howard
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| Posted: Fri Apr 29, 2005 2:18 pm Post subject: Re: Predefined class member functions and inheritance |
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"Ron Natalie" <ron (AT) spamcop (DOT) net> wrote
| Quote: | lovecreatesbeauty wrote:
Scott Meyers says that there are 6: (1)default constructor, (2)copy
constructor, (3)destructor, (4)assignment operator, (5)address-of
operator (non-const), (6)address-of operator (const), in `Effective
C++, 2nd` item 45.
If Scott actually says what you say, he's wrong. The only FUNCTIONS
provided are the default constructor, the copy constructor, the
destructor, and the copy-assignment operator.
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Scott does not say that, at least not there. I've just re-read item 45, and
he only talks about those four functions. I don't know where the OP got the
info about those two operators from, but it's not from item 45 in Effective
C++.
-Howard
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lovecreatesbeauty
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| Posted: Thu May 19, 2005 3:34 am Post subject: Re: Predefined class member functions and inheritance |
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The following changes were made for the eleventh printing of the book.
These changes apply to your copy of Effective C++, Second Edition only
if you have one of the first ten printings.
! 2/10/00 ic 212 A class declaring no operator& function(s) 9/10/01
cxh 213 does NOT have them implicitly declared. Rather,
245 compilers use the built-in address-of operator
246 whenever "&" is applied to an object of that
type. This behavior, in turn, is technically
not an application of a global operator&
function. Rather, it is a use of a built-in
operator.
I eliminated mention of operator& as an
automatically generated function and adjusted the
index to eliminate entries for the removed
material.
http://www.aristeia.com/BookErrata/ec++2e-errata_frames.html
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