C / C++ / MFC

Re: why the code can compile -- about function pointer

19-Jan-08 2:55

Hello everyone,

I am learning code from others, but I do not know why the following code section can compile?

Why assignment p = new (void (*[3])()) is ok? Are the left side and right side of assignment having compatible type?

[Code]
void (**p)();

int main()
{
p = new (void (*[3])());
return 0;
}
[/Code]

thanks in advance,
George

CPallini19-Jan-08 3:17

Re: why the code can compile -- about function pointer

19-Jan-08 3:17

Arrays names are synonim of const pointer (to the same type) hence the magic.
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.

[my articles]

George_George19-Jan-08 21:04

Re: why the code can compile -- about function pointer

19-Jan-08 21:04

Thanks CPallini!

Why "Arrays names are synonim of const pointer" could apply to my question? Could you provide more information please?

regards,
George

CPallini20-Jan-08 0:11

Re: why the code can compile -- about function pointer

20-Jan-08 0:11

George_George wrote:
void (**p)();

int main()
{
p = new (void (*[3])());
return 0;
}

void (**p)();

declares a pointer to a pointer to a function accepting no arguments and returning no arguments.

new (void (*[3])());

allocates memory for an array of pointers to functions accepting no argument and returning no value.
p can be initialised with the address of the first element of the array, i.e. with the (implicit) array name.

For instance, try the following:

void fun1() { printf("Hi");}
void fun2() { printf(" George");}

void (**p)();

int main()
{
p = new (void (*[3])());
p[0] = fun1;
p[1] = fun2;
p[2] = fun2;

p[0]();
p[1]();
p[2]();

}

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.

[my articles]

George_George20-Jan-08 0:22

20-Jan-08 0:22

Thanks CPallini,

Your sample is great! My question is answered.

regards,
George

Structured exception

George_George19-Jan-08 2:47

19-Jan-08 2:47

Hello everyone,

I am learning structured exception from,

http://msdn2.microsoft.com/en-us/library/ms681409(VS.85).aspx

I read a couple of links from MSDN, but still confused what is structured exception, what is the differences between structure exception and our normal C++ exception, like bad_alloc and various user define exception?

thanks in advance,
George

Re: Structured exception

Hamid_RT19-Jan-08 19:11

Hamid_RT

19-Jan-08 19:11

See Structured Exception Handling (C++)[^] and Microsoft Visual C++ and Win32 Structured Exception Handling
[^].

Re: Structured exception

George_George19-Jan-08 22:04

if IDCANCEL returned in DOMODAL.

19-Jan-08 22:04

Thanks Hamid,

Looks comprehensive! I just briefly read through the article and it seems structured exception is totally different from normal C++ exception. Looks like another approach to produce/handle exceptions, but I have never used and met any API in MSDN documented structured exception before.

Do you have any experience where should we use structured exception?

regards,
George

Le@rner19-Jan-08 1:02

Le@rner

19-Jan-08 1:02

if i select Cancel button, or select the Close option from the dialog box's other controls of my application are not working there is sum error how can i remove this error.

thanks and regards

CPallini19-Jan-08 1:52

19-Jan-08 1:52

v.j wrote:
there is sum error

Maybe posting the error and the affected code will help.
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.

[my articles]

Rajesh R Subramanian19-Jan-08 2:30

Rajesh R Subramanian

19-Jan-08 2:30

If you click on cancel, won't the app close? Care to explain your problem?

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

David Crow19-Jan-08 11:48

David Crow

19-Jan-08 11:48

v.j wrote:
...my application are not working there is sum error...

Would that be error A or error B?

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Paul Conrad19-Jan-08 11:53

Paul Conrad

19-Jan-08 11:53

v.j wrote:
my application are not working there is sum error

That is very poor description of your error. Without knowing what it is, no one can really help.

"I guess it's what separates the professionals from the drag and drop, girly wirly, namby pamby, wishy washy, can't code for crap types." - Pete O'Hanlon

Hamid_RT19-Jan-08 19:03

Hamid_RT

19-Jan-08 19:03

Can you more explain?

setw issue

gentleguy19-Jan-08 0:48

gentleguy

19-Jan-08 0:48

dear all

i already added in main function #include <iomanip> and using std::setw. why after i use cout statement setw(3)..no response..what happened?thanks

Li Zhiyuan

5/10/2006

Don Box19-Jan-08 1:00

Don Box

19-Jan-08 1:00

If cout is used, include iostream.h

Come online at:-
jubinc@skype

gentleguy19-Jan-08 1:23

gentleguy

19-Jan-08 1:23

already added it,any other problem? thanks

Li Zhiyuan

5/10/2006

CPallini19-Jan-08 4:37

19-Jan-08 4:37

Please post the code and state what you expect the code should do.
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.

[my articles]

Include guards vs. pragma

gentleguy20-Jan-08 1:11

gentleguy

20-Jan-08 1:11

the code is following:

double a[3][4];

for (int j = 0; j <<10; j++)
{

double a[3][4] = {{(double)rand()/RAND_MAX, (double)rand()/RAND_MAX, (double)rand()/RAND_MAX,( double)rand()/RAND_MAX},{(double)rand()/RAND_MAX,(double)rand()/RAND_MAX,(double)rand()/RAND_MAX,(double)rand()/RAND_MAX},{(double)rand()/RAND_MAX,(double)rand()/RAND_MAX,(double)rand()/RAND_MAX,(double)rand()/RAND_MAX}};

cout<< setw(3)<< "Particle" << setw(3) << j << endl << endl;
for (int i = 0; i<< 3; i++)
{
for (int j = 0; j<< 4; j++)

cout <<setw(3)<< setprecision(6) << fixed << showpoint << a[i][j]<< " ";
cout << endl;

}
cout<< endl;

}
how to save each array a and the setw is not available....

Li Zhiyuan

5/10/2006

⁷³Zeppelin18-Jan-08 19:58

⁷³Zeppelin

18-Jan-08 19:58

Anybody have an opinion on include guards:

#ifndef _thisheader_h_included
#define _thisheader_h_included

versus using pragma once?

#pragma once

I suppose the pragma directive is less portable across platforms, but is that the only issue?

Re: Include guards vs. pragma

CPallini18-Jan-08 21:32