Window is launched in the Background when the Alt key is down! - C / C++ / MFC Discussion Boards

Re: Doubt in using Math library

Maxwell Chen7-Mar-08 3:27

Maxwell Chen

7-Mar-08 3:27

CPallini wrote:
See here.

The link is broken. It is not an absolute URL.

Maxwell Chen

Re: Doubt in using Math library

CPallini7-Mar-08 3:36

CPallini

7-Mar-08 3:36

You're right but I think it was a CP bug, not mine.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

Re: Doubt in using Math library

Maxwell Chen7-Mar-08 3:59

Maxwell Chen

7-Mar-08 3:59

CPallini wrote:
it was a CP bug

Take the [PermaLink] to open a new window, and copy that new URL. It will solve! Big Grin | :-D

Maxwell Chen

Re: Doubt in using Math library

Rajkumar R7-Mar-08 4:20

Rajkumar R

7-Mar-08 4:20

Maxwell Chen wrote:
and copy that new URL. It will solve!

how's that possible, do you hacked your domain server policy [^]

Big Grin | :-D

Re: Doubt in using Math library

Maxwell Chen7-Mar-08 4:25

Maxwell Chen

7-Mar-08 4:25

Rajkumar R wrote:
how's that possible, do you hacked your domain server policy [^]

I'm home ~~~ Cool | :cool:

Maxwell Chen

Re: Doubt in using Math library

CPallini7-Mar-08 4:21

CPallini

7-Mar-08 4:21

I told you it was a CP issue. Now it's working fine without my intervention.
Big Grin | :-D

Re: Doubt in using Math library

Maxwell Chen7-Mar-08 4:25

Maxwell Chen

7-Mar-08 4:25

CPallini wrote:
I told you it was a CP issue. Now it's working fine without my intervention.

Yes, indeed! Unsure | :~

Maxwell Chen

Window is launched in the Background when the Alt key is down!

hatemtaleb6-Mar-08 21:39

hatemtaleb

6-Mar-08 21:39

Hi,

For some reason, I need to launch an application from my c++ code while holding the Alt key.
the code is really simple:

<br />
char appName[64];<br />
strcpy(appName,"c:\\WINDOWS\\notepad.exe");<br />
ShellExecute(hWnd,"open",appName,NULL,NULL,SW_SHOWNORMAL);<br />

But when executed whith the Alt key down, the application is opened behind the main window Confused | :confused:

Does anyone have any clue fro this ?

I appreciate your help.
Thanks

anti-standard code can compile -- about template class

George_George6-Mar-08 21:37

George_George

6-Mar-08 21:37

Hello everyone,

According to standard, the code should not compile.

http://gcc.gnu.org/onlinedocs/gcc/Name-lookup.html

template <typename T> struct Base {
   int i;
 };

 template <typename T> struct Derived : public Base<T> {
   int get_i() { return i; }
 };

But it can compile without any issues in Visual Studio 2008, without any warnings and even if I select disable language extensions to yes.

Any comments? What is wrong?

thanks in advance,
George

Re: anti-standard code can compile -- about template class

BadKarma6-Mar-08 21:56

BadKarma

6-Mar-08 21:56

George_George wrote:
According to standard, the code should not compile.

What do you mean with standard?
As far as I can tell the snippit looks fine. And i think that the manual is wrong on this one.
They state: In get_i(), i is not used in a dependent context according to me this is wrong since i is without any doubt the Base<T>::i which is known.

This is indeed a strange situation. Confused | :confused:

codito ergo sum

Re: anti-standard code can compile -- about template class

George_George6-Mar-08 22:30

George_George

6-Mar-08 22:30

Thanks BadKarma,

Seems like Visual Studio is wrong. Please look at section 35.19 of,

http://www.parashift.com/c++-faq-lite/templates.html#faq-35.19[^]

1.

I think this line of statement matters, agree?

--------------------
the compiler does not look in dependent base classes (like B<T>) when looking up nondependent names (like f).
--------------------

2.

What disadvantage do we have if the code can compile?

regards,
George

Re: anti-standard code can compile -- about template class

Maxwell Chen6-Mar-08 22:59

Maxwell Chen

6-Mar-08 22:59

I think current versions of VC++ treat this issue in the manner treating non-template name hiding stuff. Such as:

int a = 3;
for(int i = 0, a = 0; i < 2; i++) {
  printf("a = %d \n", a);
}
printf("a = %d \n", a);

Result:

a = 0 // The inner a
a = 3 // The outer a

Maxwell Chen

Re: anti-standard code can compile -- about template class

George_George6-Mar-08 23:22

George_George

6-Mar-08 23:22

Hi Maxwell,

1. I think Visual Studio 2008 provides correct result in the sample you provided. Are there anything wrong?

2. Does your sample have anything related to my question?

regards,
George

Re: anti-standard code can compile -- about template class

Maxwell Chen6-Mar-08 23:31

Maxwell Chen

6-Mar-08 23:31

George_George wrote:
1. I think Visual Studio 2008 provides correct result in the sample you provided. Are there anything wrong?

2. Does your sample have anything related to my question?

1. I haven't found where in the ISO C++:2003 states how this issue should be working.
But, remember?! You posted Stroustrup's words in previous thread.
And that quote matches GCC document's statement.

2. Something about name resolution ...

Maxwell Chen

Re: anti-standard code can compile -- about template class

George_George7-Mar-08 0:22

George_George

7-Mar-08 0:22

Hi Maxwell,

Thanks. What are the all possible outputs do you think the following sample you posted could give us?

http://www.codeproject.com/script/Forums/View.aspx?fid=1647&msg=2456163[^]

regards,
George

Re: anti-standard code can compile -- about template class

BadKarma6-Mar-08 22:59

BadKarma

6-Mar-08 22:59

George_George wrote:
Seems like Visual Studio is wrong. Please look at section 35.19 of,

http://www.parashift.com/c++-faq-lite/templates.html#faq-35.19[^]

1.I think this line of statement matters, agree?

--------------------
the compiler does not look in dependent base classes (like B<t> when looking up nondependent names (like f).
--------------------

This is correct Visual Studio compiles the non-valid code without any troubles

George_George wrote:
2. What disadvantage do we have if the code can compile?

Thats a hard one since Visual Studio compiles and provides the correct solution. Even when there are global variables or function is correctly understand what the programmer wants and does a check the base class first.

This brings us too two other questions one might ask.
1. Can one write code which breaks this rule? Meaning, can on write code that explicit calls the global function instead of the base function?
2. If this is not possible, why does the rule: the compiler does not look in dependent base classes (like B<t> when looking up nondependent names (like f). exist? Is it because older compilers where not smart enough to clear this up?

codito ergo sum

Re: anti-standard code can compile -- about template class

Maxwell Chen6-Mar-08 23:06

Maxwell Chen

6-Mar-08 23:06

The intention Stroustrup and the ISO C++ team defined this seems because they hoped to avoid the "nasty macro-like behaviours" (see George's previous thread).

Maxwell Chen

Re: anti-standard code can compile -- about template class

George_George6-Mar-08 23:24

George_George

6-Mar-08 23:24

Hi Maxwell,

I understand what means "nasty macro-like behaviours", but I do not think "nasty macro-like behaviours" is similar to my sample in original question?

regards,
George

Re: anti-standard code can compile -- about template class

Maxwell Chen6-Mar-08 23:35

Maxwell Chen

6-Mar-08 23:35

George_George wrote:
I understand what means "nasty macro-like behaviours", but I do not think "nasty macro-like behaviours" is similar to my sample in original question?

Your sample in the original question in this thread originated from your previous thread quoting Stroustrup's words. You forgot?! Unsure | :~

Maxwell Chen

Re: anti-standard code can compile -- about template class

Maxwell Chen6-Mar-08 23:41

Maxwell Chen

6-Mar-08 23:41

Don't push me doing copy-and-paste!! Laugh | :laugh:

Maxwell Chen

Re: anti-standard code can compile -- about template class

George_George7-Mar-08 0:21

George_George

7-Mar-08 0:21

What do you mean, Maxwell?

regards,
George

Re: anti-standard code can compile -- about template class

Maxwell Chen7-Mar-08 3:09

Maxwell Chen

7-Mar-08 3:09

George_George wrote:
What do you mean, Maxwell?

(I am home, so I can copy-and-paste now! )

In the beginning, you quoted Stroustrup's words.

Not can an unqualified name used in a template
 ever be bound to a local name. Finally, even if a template
 is first used within a class, unqualified names used in the template
 will not be bound to members of that class.
 Ignoring lcoal names is essential to prevent a lot of
 nasty macro-like behavior.
  
section C.18.3.3 Point of Instantiation Binding

So I gave you that GCC document[^], which introduced this code sample.
Doesn't the code match what Stroustrup said?! Unsure | :~

template <typename T> 
struct Base {
  int i;
};
template <typename T> 
struct Derived : public Base<T> {
  int get_i() { return i; } // Even if a template is first used within a class, 
                            //  <font color="red">unqualified names</font> used in the template
                            //  will <font color="red">not be bound to members</font> of that class. 
};

Maxwell Chen

Re: anti-standard code can compile -- about template class

George_George7-Mar-08 3:18

George_George

7-Mar-08 3:18

Thanks Maxwell,

I am interested about your points,

--------------------
Even if a template is first used within a class, unqualified names used in the will not be bound to members of that class.
--------------------

To make discussion clear, could you let me know,

1. what is a template do you refer to in the sample?

2. what is the class (within a class) do you refer to in the sample?

3. what is the unqualified names do you refer to in the sample?

4. what is the "members of that class" do you refere to in the sample?

regards,
George

Re: anti-standard code can compile -- about template class

Maxwell Chen7-Mar-08 3:23

Maxwell Chen

7-Mar-08 3:23

George_George wrote:
1. what is a template do you refer to in the sample?

2. what is the class (within a class) do you refer to in the sample?

3. what is the unqualified names do you refer to in the sample?

4. what is the "members of that class" do you refere to in the sample?

1. You saw the keyword template.

2. A struct is a class with members being public by default.

3. That i.

4. That i is the member of the struct (class).

Maxwell Chen

Re: anti-standard code can compile -- about template class

George_George7-Mar-08 3:37

George_George

7-Mar-08 3:37

Thanks Maxwell,

I am confused about your points 1 and 2. Smile | :)

I can not believe when Bjarne said "Even if a template is first used within a class", he means even if a template keyword? is first used within a class? It should be some specific template, right?

Should it mean even if template Base<t> first used within a class Derived<t>?

Maxwell Chen wrote:
1. You saw the keyword template.

2. A struct is a class with members being public by default.

regards,
George

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