Explicit Virtual Functions

[Sarath]

Hi All,

Could you please give some good links to learn about the "Proposed new
syntax for Virtual functions" in the new standard?

If you could explain it in simple manner as a reply that will be very
helpful. I just referred Wikipedia for the same. But still looking for
a simple description for same.

Regards,
Sarath

[John Harrison]

Re: Explicit Virtual Functions

Sarath wrote:

Hi All,
>
Could you please give some good links to learn about the "Proposed new
syntax for Virtual functions" in the new standard?
>
If you could explain it in simple manner as a reply that will be very
helpful. I just referred Wikipedia for the same. But still looking for
a simple description for same.
>
Regards,
Sarath
>

This is official

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2108.html

and seems easy enough. It's just a machanism for avoiding mistakes when
writing a derived class.

Can't say I like it very much at first glance.

john

[Sarath]

Re: Explicit Virtual Functions

On Mar 4, 6:49 pm, John Harrison <john_androni.. .@hotmail.comwr ote:

Sarath wrote:

Hi All,

>

Could you please give some good links to learn about the "Proposed new
syntax for Virtual functions" in the new standard?

>

If you could explain it in simple manner as a reply that will be very
helpful. I just referred Wikipedia for the same. But still looking for
a simple description for same.

>

Regards,
Sarath

>
This is official
>

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2108.html

>
and seems easy enough. It's just a machanism for avoiding mistakes when
writing a derived class.
>
Can't say I like it very much at first glance.
>
john

I'm really confused with one of the explanation I found in Wikipedia

http://en.wikipedia.org/wiki/C++0x#Explicit_syntax_for_virtual_functions

I think these are ablsolutely different one.

[John Harrison]

Re: Explicit Virtual Functions

Sarath wrote:

On Mar 4, 6:49 pm, John Harrison <john_androni.. .@hotmail.comwr ote:
>

>>Sarath wrote:
>>

>>>Hi All,

>>

>>>Could you please give some good links to learn about the "Proposed new
>>>syntax for Virtual functions" in the new standard?

>>

>>>If you could explain it in simple manner as a reply that will be very
>>>helpful. I just referred Wikipedia for the same. But still looking for
>>>a simple description for same.

>>

>>>Regards,
>>>Sarath

>>
>>This is official
>>
>>http://www.open-std.org/jtc1/sc22/wg...006/n2108.html
>>
>>and seems easy enough. It's just a machanism for avoiding mistakes when
>>writing a derived class.
>>
>>Can't say I like it very much at first glance.
>>
>>john

>
>
>
I'm really confused with one of the explanation I found in Wikipedia

http://en.wikipedia.org/wiki/C++0x#Explicit_syntax_for_virtual_functions

>
I think these are ablsolutely different one.
>

Yep, they seem to be tackling the same issue but in very different ways.

[Pete Becker]

Re: Explicit Virtual Functions

Sarath wrote:

>
I'm really confused with one of the explanation I found in Wikipedia

http://en.wikipedia.org/wiki/C++0x#Explicit_syntax_for_virtual_functions

>

That's not surprising: the explanation is quite muddled.

--

-- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)

[Sarath]

Re: Explicit Virtual Functions

On Mar 5, 12:45 am, Pete Becker <p...@versatile coding.comwrote :

Sarath wrote:
>

I'm really confused with one of the explanation I found in Wikipedia
http://en.wikipedia.org/wiki/C++0x#E...tual_functions

>
That's not surprising: the explanation is quite muddled.
>
--
>
-- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)

yea.. that's a bit difficult to understand. but the original proposal
(http://www.open-std.org/jtc1/sc22/wg...006/n2108.html -
posted John harrison ) is lacking of good examples. Anyway I
understood somewhat from it but when thinking about WIkipedia example
it makes me confused.

It seems that the example said in Wikipedia follows the syntax
proposed early by Bjarne Stroustrup

[bjarne]

Re: Explicit Virtual Functions

On Mar 4, 10:45 am, "Sarath" <CSar...@gmail. comwrote:

>
It seems that the example said in Wikipedia follows the syntax
proposed early by BjarneStroustru p

Not guilty (for a change). That's not one of my proposals.

Please note that the C++0x design is still in a flux and that you
can't be certain of details until the votes are done. The wikkipedia
entry seems a bit "optimistic "/certain in places. For example, there
is no guarantee that any new facility for controlling overriding will
be added.

[Sarath]

Re: Explicit Virtual Functions

On Mar 5, 7:48 am, "bjarne" <bjarne@gmail.c omwrote:

On Mar 4, 10:45 am, "Sarath" <CSar...@gmail. comwrote:
>
>
>

It seems that the example said in Wikipedia follows the syntax
proposed early by BjarneStroustru p

>
Not guilty (for a change). That's not one of my proposals.
>
Please note that the C++0x design is still in a flux and that you
can't be certain of details until the votes are done. The wikkipedia
entry seems a bit "optimistic "/certain in places. For example, there
is no guarantee that any new facility for controlling overriding will
be added.

Sorry sir,
It was my assumption when I saw an alternative syntax. In the

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2108.html

proposal it is also indicating about the alternative syntax specified
you(Rationale section)... So I thought it other way. Sorry for my
misinterpretati on.

[Dave Rahardja]

Re: Explicit Virtual Functions

On 4 Mar 2007 05:52:40 -0800, "Sarath" <CSarath@gmail. comwrote:

>On Mar 4, 6:49 pm, John Harrison <john_androni.. .@hotmail.comwr ote:

>Sarath wrote:

Hi All,

>>

Could you please give some good links to learn about the "Proposed new
syntax for Virtual functions" in the new standard?

>>

If you could explain it in simple manner as a reply that will be very
helpful. I just referred Wikipedia for the same. But still looking for
a simple description for same.

>>

Regards,
Sarath

>>
>This is official
>>
>http://www.open-std.org/jtc1/sc22/wg...006/n2108.html
>>
>and seems easy enough. It's just a machanism for avoiding mistakes when
>writing a derived class.
>>
>Can't say I like it very much at first glance.
>>
>john

>
>
>I'm really confused with one of the explanation I found in Wikipedia
>http://en.wikipedia.org/wiki/C++0x#E...tual_functions
>
>I think these are ablsolutely different one.

Is there really a need for controlling which virtual functions can be
specialized? What is the class of problems that this is supposed to solve?

I think that a syntax addition that explicitly indicates that a derived class
is specializing a base class's virtual function is very useful. The absence of
such indications should result in a warning only (to preserve compatibility
with old code).

I especially like


class B
{
public:
virtual void foo() {}
};

class D: public D
{
public:
virtual void foo(): B {}
};


It's clean.

-dr

[Sarath]

Re: Explicit Virtual Functions

On Mar 6, 12:17 pm, Dave Rahardja
<drahardja_atsi gn_pobox_dot_.. .@pobox.comwrot e:

On 4 Mar 2007 05:52:40 -0800, "Sarath" <CSar...@gmail. comwrote:
>
>
>
>
>

On Mar 4, 6:49 pm, John Harrison <john_androni.. .@hotmail.comwr ote:

Sarath wrote:
Hi All,

>

Could you please give some good links to learn about the "Proposed new
syntax for Virtual functions" in the new standard?

>

If you could explain it in simple manner as a reply that will be very
helpful. I just referred Wikipedia for the same. But still looking for
a simple description for same.

>

Regards,
Sarath

>

This is official

>

>http://www.open-std.org/jtc1/sc22/wg...006/n2108.html

>

and seems easy enough. It's just a machanism for avoiding mistakes when
writing a derived class.

>

Can't say I like it very much at first glance.

>

john

>

I'm really confused with one of the explanation I found in Wikipedia
http://en.wikipedia.org/wiki/C++0x#E...tual_functions

>

I think these are ablsolutely different one.

>
Is there really a need for controlling which virtual functions can be
specialized? What is the class of problems that this is supposed to solve?
>
I think that a syntax addition that explicitly indicates that a derived class
is specializing a base class's virtual function is very useful. The absence of
such indications should result in a warning only (to preserve compatibility
with old code).
>
I especially like
>
class B
{
public:
virtual void foo() {}
>
};
>
class D: public D
{
public:
virtual void foo(): B {}
>
};
>
It's clean.
>
-dr- Hide quoted text -
>
- Show quoted text -

that's a nice proposal :D

[frege]

Re: Explicit Virtual Functions

On Mar 5, 10:17 pm, Dave Rahardja
<drahardja_atsi gn_pobox_dot_.. .@pobox.comwrot e:

>
I especially like
>
class B
{
public:
virtual void foo() {}
>
};
>
class D: public D
{
public:
virtual void foo(): B {}
>
};
>
It's clean.
>

Microsoft (VC 8) already allows B::foo(). ie:

class D: public B
{
public:
virtual void B::foo() {}
>
};
>

if B does not have a matching foo, it issues an error.

-dr

Tony

[Sarath]

Re: Explicit Virtual Functions

On Mar 6, 1:34 pm, "frege" <gottlobfr...@g mail.comwrote:

On Mar 5, 10:17 pm, Dave Rahardja
>
>
>
>
>
<drahardja_atsi gn_pobox_dot_.. .@pobox.comwrot e:
>

I especially like

>

class B
{
public:
virtual void foo() {}

>

};

>

class D: public D
{
public:
virtual void foo(): B {}

>

};

>

It's clean.

>
Microsoft (VC 8) already allows B::foo(). ie:
>

class D: public B
{
public:
virtual void B::foo() {}

>

};

>
if B does not have a matching foo, it issues an error.
>

-dr

>
Tony- Hide quoted text -
>
- Show quoted text -

Yea VC 8 has really some new useful improvement in both language and
syntax.

In the case of overriding they have introduced some new keywords,
clean and elegant syntax.

http://msdn2.microsoft.com/en-us/library/4dd87x3d.aspx
http://msdn2.microsoft.com/en-us/library/fw0bbh51.aspx

[Pete Becker]

Re: Explicit Virtual Functions

Dave Rahardja wrote:

On 4 Mar 2007 05:52:40 -0800, "Sarath" <CSarath@gmail. comwrote:
>

>On Mar 4, 6:49 pm, John Harrison <john_androni.. .@hotmail.comwr ote:

>>Sarath wrote:
>>>Hi All,
>>>Could you please give some good links to learn about the "Proposed new
>>>syntax for Virtual functions" in the new standard?
>>>If you could explain it in simple manner as a reply that will be very
>>>helpful. I just referred Wikipedia for the same. But still looking for
>>>a simple description for same.
>>>Regards,
>>>Sarath
>>This is official
>>>
>>http://www.open-std.org/jtc1/sc22/wg...006/n2108.html
>>>
>>and seems easy enough. It's just a machanism for avoiding mistakes when
>>writing a derived class.
>>>
>>Can't say I like it very much at first glance.
>>>
>>john

>>
>I'm really confused with one of the explanation I found in Wikipedia
>http://en.wikipedia.org/wiki/C++0x#E...tual_functions
>>
>I think these are ablsolutely different one.

>
Is there really a need for controlling which virtual functions can be
specialized? What is the class of problems that this is supposed to solve?
>

Despite it's misuse in that article, "specialize d" is not the right
term. A function with the same signature as a virtual function in a base
class overrides that function.

I think that a syntax addition that explicitly indicates that a derived class
is specializing a base class's virtual function is very useful. The absence of
such indications should result in a warning only (to preserve compatibility
with old code).
>
I especially like
>
>
class B
{
public:
virtual void foo() {}
};
>
class D: public D
{
public:
virtual void foo(): B {}
};
>
>
It's clean.
>

Yup. And you'll have lots of fun playing "Mother, may I?" with the compiler.

--

-- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)

[tragomaskhalos]

Re: Explicit Virtual Functions

On Mar 6, 8:16 am, "Sarath" <CSar...@gmail. comwrote:

Yea VC 8 has really some new useful improvement in both language and
syntax.
>
In the case of overriding they have introduced some new keywords,
clean and elegant syntax.
>
http://msdn2.microsoft.com/en-us/library/4dd87x3d.aspx
http://msdn2.microsoft.com/en-us/library/fw0bbh51.aspx
>

Big caveat here : Microsoft are notoriosly bad at distinguishing
between C++ and C++/CLI in their documentation.
These links seem to refer to C++/CLI.

[Dave Rahardja]

Re: Explicit Virtual Functions

On Tue, 06 Mar 2007 07:15:29 -0500, Pete Becker <pete@versatile coding.com>
wrote:

>Is there really a need for controlling which virtual functions can be
>specialized? What is the class of problems that this is supposed to solve?
>>

>
>Despite it's misuse in that article, "specialize d" is not the right
>term. A function with the same signature as a virtual function in a base
>class overrides that function.

You're right. It's override, not specialize.

>

>I think that a syntax addition that explicitly indicates that a derived class
>is specializing a base class's virtual function is very useful. The absence of
>such indications should result in a warning only (to preserve compatibility
>with old code).
>>
>I especially like
>>
>>
>class B
>{
>public:
> virtual void foo() {}
>};
>>
>class D: public D
>{
>public:
> virtual void foo(): B {}
>};
>>
>>
>It's clean.
>>

>
>Yup. And you'll have lots of fun playing "Mother, may I?" with the compiler.

This argument can be said about many features that enforce tighter semantic
controls in the language. Truth be told, I have encountered so many errors in
which the author of a derived class /thought/ that he'd overridden a virtual
function in a base class, but actually created a slightly different version
instead. Hours of fun debugging ensued. The explicit syntax would be helpful.

I suppose the warning could be restricted to the occasions where you are
hiding a base class virtual function by defining a function of the same name
(but with different parameters) in the derived class. That way classes that
/correctly/ override base class virtual functions will not generate warnings.

-dr