C / C++ / MFC Discussion Boards

Re: can i debug multi threading application?

Hamid_RT7-May-07 9:24

Hamid_RT

7-May-07 9:24

Your answer is exactly to question very similar Laugh | :laugh:

but whats meaning of "Yo"?

WhiteSky

Re: can i debug multi threading application?

super_ttd9-May-07 3:58

super_ttd

9-May-07 3:58

by "Yo", he meant "Ya" with a mouth getting closed... get what i mean ? Wink | ;)

Constant pointer

ragavan7-May-07 1:24

ragavan

7-May-07 1:24

Hi Can anyone tell me the difference between constant pointer and pointer to a constant. Please tell me the situation in which they are used.

Thanks in advance

Re: Constant pointer

Cedric Moonen7-May-07 1:31

Cedric Moonen

7-May-07 1:31

See here[^]

Cédric Moonen
Software developer

Charting control [v1.2]

Re: Constant pointer

toxcct7-May-07 1:44

toxcct

7-May-07 1:44

ragavan wrote:
difference between constant pointer and pointer to a constant

isn't what you say descriptive enough ?! Big Grin | :-D

a const pointer cannot be modified, while a pointer to const points to a memory ary which is read-only

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Re: Constant pointer

Michael Dunn7-May-07 8:45

Michael Dunn

7-May-07 8:45

[18.5] What's the difference between "const Fred* p", "Fred* const p" and "const Fred* const p"?[^]

--Mike--
Visual C++ MVP Cool | :cool:

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Dunder-Mifflin, this is Pam.

overloading new operator

ragavan7-May-07 1:23

ragavan

7-May-07 1:23

Hi Can anyone tell me why it is necessary to overload new and delete operator

Thanks in advance

Re: overloading new operator

Cedric Moonen7-May-07 1:26

Cedric Moonen

7-May-07 1:26

ragavan wrote:
Can anyone tell me why it is necessary to overload new and delete operator

It is certainly not necessary to overload these operators. It can be done, sure, but it is never needed. I never did that myself (and I don't see a reason why I would do so).

An example of what you can do by overloading these operators is what MFC does: it allows to track memory leaks.

Cédric Moonen
Software developer

Charting control [v1.2]

Re: overloading new operator

Hans Dietrich7-May-07 1:40

Hans Dietrich

7-May-07 1:40

Well put.

It seems like the OP meant to say "when it is necessary" rather than "why it is necessary".

Re: overloading new operator

James R. Twine7-May-07 3:26

James R. Twine

7-May-07 3:26

Cedric Moonen wrote:
It is certainly not necessary to overload these operators. It can be done, sure, but it is never needed. I never did that myself (and I don't see a reason why I would do so).

Yikes! Please be careful saying things like this to less-experienced developers - just because you never had a reason to do so does not mean that one does not exist. :P

Cedric Moonen wrote:
An example of what you can do by overloading these operators is what MFC does: it allows to track memory leaks.

Unless MFC changed recently, I believe this was mostly done by the use of DEBUG_NEW instead of new, and this in turn happened thanks to a #define that was in effect for debug builds. That is not really overloading new...

Peace!

-=- James
Please rate this message - let me know if I helped or not!<HR>If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
See DeleteFXPFiles

Re: overloading new operator

Cedric Moonen7-May-07 7:28

Cedric Moonen

7-May-07 7:28

James R. Twine wrote:
Yikes! Please be careful saying things like this to less-experienced developers - just because you never had a reason to do so does not mean that one does not exist.

That was certainly not my intention. Maybe I expressed myself badly.

Cédric Moonen
Software developer

Charting control [v1.2]

Re: overloading new operator

toxcct7-May-07 1:42

toxcct

7-May-07 1:42

ragavan wrote:
why it is necessary to overload new and delete operator

to put some extra printf() inside them for instance !? Wink | ;)

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Re: overloading new operator

James R. Twine7-May-07 3:12

James R. Twine

7-May-07 3:12

   One (the only?) reason is when the objects need to be allocated in a non-standard way. For example, for performance reasons, you may be using per-thread heaps so as to avoid heap contention in a multi-threaded application (if the application is allocation intensive).

   Or if you have to allocate lots of smaller-sized objects (< 16-32 bytes) and you need to optimize the allocations by allocating larger blocks and then chunking them yourself. Combining the Win32 heap's and C-RTL's overhead, a heap allocation can have between 20-32 bytes of overhead. So if you need to allocate one million objects of 8 bytes each, this overhead (both space and execution time) can start to add up quickly.

   Granted, the average everyday developer does not need to be (or simply is not) concerned with such things, but those are some reasons I have done it in the past.

   Peace!

CListCtrl

study.sourabh7-May-07 0:43

study.sourabh

7-May-07 0:43

Hi,

i have a CListView style of which is in report.
how can i get the cell which user selected?
Is it posible to change the icone used for check box ?

thanks in advance
Sourabh

sourabh

Re: CListCtrl

Hans Dietrich7-May-07 1:31

Hans Dietrich

7-May-07 1:31

study.sourabh wrote:
how can i get the cell which user selected?

In my XListCtrl, I have the function:

int CXListCtrl::GetCurSel()
{
	POSITION pos = GetFirstSelectedItemPosition();
	int nSelectedItem = -1;
	if (pos != NULL)
		nSelectedItem = GetNextSelectedItem(pos);
	return nSelectedItem;
}

Note that this returns the selected row. To find out which column was clicked, you can handle the NM_CLICK or LVN_COLUMNCLICK messages.

study.sourabh wrote:
Is it posible to change the icone used for check box ?

Yes, you can handle the NM_CUSTOMDRAW message and draw your own. There are examples here on CP that will help.

Best wishes,
Hans

Re: CListCtrl

study.sourabh7-May-07 3:03

study.sourabh

7-May-07 3:03

hi Hans,
Thanks for the help.
But LVN_COLUMNCLICK message will give the colem which was selected in the header of CListCtrl right?
i wanted to know to which cell in the row user selected.Is it posible to get information regarding that?
thnanks

sourabh

Re: CListCtrl

Hans Dietrich7-May-07 3:36

Hans Dietrich

7-May-07 3:36

As I said, you can handle the NM_CLICK message. Here is some sample code:

void CXListCtrlTestDlg::OnClick(NMHDR* pNMHDR, LRESULT* pResult)
{
	LPNMITEMACTIVATE pNMIA = reinterpret_cast<LPNMITEMACTIVATE>(pNMHDR);
	int nItem = -1;
	int nSubItem = -1;
	if (pNMIA)
	{
		nItem = pNMIA->iItem;
		nSubItem = pNMIA->iSubItem;
	}

	if (nItem >= 0 && nSubItem >= 0)
	{
		CString strText = m_List.GetItemText(nItem, nSubItem);
		Log(_T("OnClick at (%d,%d):  '%s'"), nItem, nSubItem, strText);
	}

	*pResult = 0;
}

Best wishes,
Hans

Re: CListCtrl

study.sourabh7-May-07 18:02

study.sourabh

7-May-07 18:02

Hi Hans,

Thank you very much.
It works i get the column which is clicked.

sourabh

NP-complete riddle/algorithm

Yariv6-May-07 23:56

Yariv

6-May-07 23:56

I'm looking for a c/c++ solution for the following NP-completeness problem:

Write a function that gets an array of integers, its size and an integer. The function should return true if the sum of any subset of the array members is equalt to the integer. For example, if the array is 1,3,5,6 then possible sum are 4(1+3),11(5+6),9(1+3+5). If the intefger is 20 then the function returns false (no way of getting a sum higher than 15:1+3+5+6)

C Function declaration for example: bool is_subset(int* pArray,int nSize,int Sum)
MFC function declaration for example: BOOL IsSubset(const CUIntArray& Array,UINT Sum)

Thanks

Re: NP-complete riddle/algorithm

toxcct7-May-07 0:04

toxcct

7-May-07 0:04

have you already started to code something by yourself on this assignement ?
or are you a bit too lazy to expecting us to do your homework ? Poke tongue | ;-P

also, please ask a specific question; asking for a whole job is all but what will bring you some help, because people here are not paid for helping, and get iritated by lazy questions...

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Re: NP-complete riddle/algorithm

Yariv7-May-07 8:47

Yariv

7-May-07 8:47

Please look at my reply to Hans...
Thanks

Re: NP-complete riddle/algorithm

Hans Dietrich7-May-07 1:36

Hans Dietrich

7-May-07 1:36

That sounds like a neat assignment. Just out of curiosity, what grade level are you in?

BTW, there are more possible sums than what you list.

Best wishes,
Hans

Re: NP-complete riddle/algorithm

Yariv7-May-07 8:46

Yariv

7-May-07 8:46

Luckily I'm not a student. I guess that if I was I had the answer because it sounds like a school assignment. I'm a shame to admit that when I was this question was introduced to me I started to write it using a recursive function, but I got stuck because it started to be too complex. It was then that I thought there must be a simple (school) solution for this, as this is an academic riddle (just like the traveling salesman). I thought mayeb someone here has the insight...

Re: NP-complete riddle/algorithm

Yariv7-May-07 12:43

Yariv

7-May-07 12:43

Incase someone interested, here is a simple solution. I have no idea why I got stuck from the first place:

<br />
BOOL IsSum(const CUIntArray& Array,UINT Sum) const<br />
{<br />
	for(int i=0;i < Array.GetSize();i++)<br />
	{<br />
		if(Array[i] == Sum)<br />
			return TRUE;<br />
		else if(Array[i] < Sum)<br />
		{<br />
			if(CheckSum(Array,Sum,i,Array[i]))<br />
				return TRUE;<br />
		}<br />
	}<br />
	return FALSE;<br />
}<br />
<br />
BOOL CheckSum(const CUIntArray& Array,UINT Sum,int nIndex,UINT SoFar) const<br />
{<br />
  for(int i=nIndex+1;i < Array.GetSize();i++)<br />
 {<br />
   if((SoFar+Array[i]) == Sum)<br />
     return TRUE;<br />
   else if((SoFar+Array[i])<Sum)<br />
   {<br />
      if(CheckSum(Array,Sum,i,SoFar+Array[i]))<br />
         return TRUE;<br />
   }<br />
 }	<br />
 return FALSE;<br />
}<br />

ScrollBar Presence in ListBox ?

sayed_76-May-07 23:30

sayed_7

6-May-07 23:30

Hi I have one enquiry. I am a novice in mfc. Using one listbox. In that sometimes I have less data, some times lot of data. Depending on that the scrollbar comes automatically. So my enquiry is that is there any way to know the presence of scrollbar in the listbox? If so how to do that ? Any suggession will be highly helpful.

Regardly
Confused | :confused:

Sayed

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