C / C++ / MFC

Re: center text in title bar of app.(Found the link)

8-May-03 6:14

Hi,
there was a working code on the net called "shadcap", originally written by "Paul DiLascia", Q&A author of MSJ Magaizine. Please search it on the net. Actually, I downloaded the code, just few days back. I couldnt find the link now. Please search it on the net. Otherwise, I can send u the code.

Hari Krishnan (Noida)8-May-03 6:22

C++ Function objects - how to use them?

8-May-03 6:22

Hi,
As, other members were suggested, its bit of complex coding.
If you really want to do it, here is the link, and
download "C++0697.exe"

http://www.microsoft.com/msj/0697/c0697.aspx

regards
~Hari~

Ilushka8-May-03 2:37

Ilushka

8-May-03 2:37

Hi All!

Here goes the question:

Mr. C++ has cleary descibed how to use function objects in Parhagraph 18.4 of his Book. The
Sample code works OK, and if i use them with STL, everything`s OK

Here is a simple sample:

void Add7(int& out_Int)
{
out_Int += 7;
}

class AddNumber
{
public:
int m_iToAdd;

AddNumber(int in_iToAdd = 0)
{
m_iToAdd = in_iToAdd;
}

void operator()(int& out_Int)
{
out_Int += m_iToAdd;
}
};

class A
{
public:
std::vector < int > m_vData;
};

void main()
{

A tmp_a;

tmp_a.m_vData.push_back(7);
tmp_a.m_vData.push_back(5);
tmp_a.m_vData.push_back(6);

std::for_each(tmp_a.m_vData.begin(),tmp_a.m_vData.end(),Add7);

std::for_each(tmp_a.m_vData.begin(),tmp_a.m_vData.end(),AddNumber(13));

}

---

But when i try to use them some other way than in combination with STL, I get that:

typedef void (*TraveseFuncPtr) (int&);

void Add7(int& out_Int)
{
out_Int += 7;
}

class AddNumber
{
public:
int m_iToAdd;

AddNumber(int in_iToAdd = 0)
{
m_iToAdd = in_iToAdd;
}

void operator()(int& out_Int)
{
out_Int += m_iToAdd;
}
};

class A
{
public:
std::vector < int > m_vData;
void TraverseVector(TraveseFuncPtr in_func)
{
for (int i = 0; i < m_vData.size(); i++)
{
(*in_func)(m_vData[i]);
}
}
};

void main()
{
A tmp_a;

tmp_a.m_vData.push_back(7);
tmp_a.m_vData.push_back(5);
tmp_a.m_vData.push_back(6);

tmp_a.TraverseVector(Add7); // All ok.

tmp_a.TraverseVector(AddNumber(13)); //C2664
}

---

And thats it.

error C2664: 'TraverseVector' : cannot convert parameter 1 from 'class AddNumber' to 'void (__cdecl *)(int &)'
No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

I tried to dig up STL source but hell the same for_each takes a CLASS (!) as a template parameter.
No functions there.

Who can say anything to this?

Sincerely yours, Ilya Kalujny.

Aaron Schaefer8-May-03 3:42

Aaron Schaefer

8-May-03 3:42

Yes, but what you have defined as the argument to the TraverseVector is simplay a function pointer:

typedef void (*TraveseFuncPtr) (int&);

Function pionters are not quite the same thing as function objects. If you want to define a function that accepts as a parameter a functor (some class which has an overloaded operator()), then you could make the function a template function and have the exact type of the class you wold pass in a template parameter.

Maybe something like this:

template<class _functortype="">
void TraverseVector(_FunctorType in_func)
{
for (int i = 0; i < m_vData.size(); i++)
{
in_func(m_vData[i]);
}
}

This should allow you to pass in an aribtrary type as an argument, so long as it had an overloaded operator() with the correct signature.

jhwurmbach8-May-03 3:47

jhwurmbach

8-May-03 3:47

One question:
Isn't a function object (also named Functor) an object which behaves like a function?.
That means this object has an overloaded operator() returning whatever the object does.
This could be the explanation why the STL wants a CLASS - it calls its operator().

For your Add7-Object it would look about like

class Add7() 
{
int operator()(int& out_Int)const 
  {
    return out_Int + 7;
  };
}

This can be further complicated by making the class Add7 a template.

My opinions may have changed, but not the fact that I am right.

Andrew Walker8-May-03 3:50

Andrew Walker

8-May-03 3:50

One way to do what you want would be to make the traverse vector method a template method. I recommend against doing this, using STL means using all (or as much as you can manage) of it - so you should attempt to reuse tools like for_each wherever you can. for_each works along the same lines as the attached code, but may be optomised by the library for some template specialisations.

The problem, passing extra information to a functor (function object), that you're putting forward is quite common, binders are a good place to look if you're interested in more generic solutions to this problem.

class A <br />
{<br />
public:<br />
	std::vector < int > m_vData;<br />
<br />
	template<class F><br />
	void TraverseVector(F in_func) <br />
	{<br />
		for (int i = 0; i < m_vData.size(); i++) <br />
		{<br />
			in_func(m_vData[i]);<br />
			cout << m_vData[i] << endl;<br />
		}<br />
	}<br />
<br />
};

John R. Shaw8-May-03 17:15

John R. Shaw

8-May-03 17:15

You are not passing a pointer to a function:
tmp_a.TraverseVector(AddNumber(13));
(passing the return value of AddNumber(13) to TraverseVector(), which is void/nothing/nada).

This is passing a pointer to a function:
tmp_a.TraverseVector(AddNumber);

Trust in the code Luke. Yea right!

Menu sharing in MDI application with 2 document templates

kuhx198011-May-03 4:16

kuhx1980

11-May-03 4:16

the definition of std::for_each

template <class InputIterator, class Function>
Function for_each (InputIterator first, InputIterator last, Function f)

so, you can do this:
// =======================================================
class A
{
public:
std::vector <int> m_vData;
template <class Function> // add this
void TraverseVector(Function in_func) // ******
{
for (int i = 0; i < m_vData.size(); i++)
{
(*in_func)(m_vData[i]);
}
}
};
// =======================================================

Jayanta Basu8-May-03 2:27

Jayanta Basu

8-May-03 2:27

I have an MDI application witn 2 document templates (with 1 or more child windows normally open). One child window is of one type while there can be multiple child windows of the other type.

I would like to have a common menu independant of the active child window. The problem I am facing is of updation of status of the menu (checked/ unchecked etc). Apparently, the menu displayed is that of the active child frame. Presently, I have the identical menu for both document types.

Is there any standard method to synchronize the menu for the both the frames?

Thanks

Jayanta Basu

writing data to a text file?????????

xxhimanshu8-May-03 1:43

xxhimanshu

8-May-03 1:43

hi all,
I want to write some data to a existing text file...I am using ATL...I dont have any clue..can anyone help and tell me how to proceed..any help or pointers are highly appreciated..
thanks in advance

Himanshu

Re: writing data to a text file?????????

Nitron8-May-03 1:55

Nitron

8-May-03 1:55

std::ofstream outFile(szFilename, ios::out | ios::app);

outFile << "Your Text Here!";

outFile.close();

- Nitron

"Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

Can someone help, im new to C++

mawmany2k8-May-03 1:30

mawmany2k

8-May-03 1:30

I have a string containing the sentence: "a do cat from hello thomas d"

My task is to read through the string, determine what is the shortest word(s) and what is the longest word(s) then display each.

So for the sentence above, i will need to display the following:

Biggest word(s)= thomas
Smallest word(s) = a, d

The problem i have is determining the longest and shortest word(s).

This is my first attempt at C++ after Java for 6 months before i changed my course at college

Please help me

..::M::..

Re: Can someone help, im new to C++

Stephane Rodriguez.8-May-03 1:33

Stephane Rodriguez.

8-May-03 1:33

The simplest way to do it is to use the MFC CString class. It's much like the Java String.

Create a new project, choose MFC application, then dialog-based. From this point, you can use the MFC CString class.

Re: Can someone help, im new to C++

Hari Krishnan (Noida)8-May-03 2:17

8-May-03 2:17

Hi,
Try with following code snippet.

----------------------------------------------------------
Smile | :)

CString strSentence = "a do cat from hello thomas d";
int iLongest = 0; //Initialize with minimum value.
int iShortest = 1024; //Initialize with Big Value
int nIndex;

//Backup. If you dont want you can remove
CString strHelper(strSentence);

while(!strHelper.IsEmpty())
{
if(-1 == (nIndex = strHelper.Find(' ', 0)))
{
nIndex = strHelper.GetLength(); //Last word
strHelper.Empty();
}
if(nIndex < iShortest)
iShortest = nIndex;
if(nIndex > iLongest)
iLongest = nIndex;

strHelper.Delete(0, nIndex+1); //Remove including space.
}
----------------------------------------------------------

Memory Leak

saravanaram8-May-03 1:09

saravanaram

8-May-03 1:09

Hi all,
in mfc dialog based application i have the following function.

void Reverse()
{
// TODO: Add your control notification handler code here
int nIndex, nStrLength, nWordIndex;
TCHAR *pStrWord, *pStrFinal, ch;

UpdateData(TRUE);

nStrLength = m_strInput.GetLength();

pStrWord = new TCHAR [nStrLength + 1];
pStrFinal = new TCHAR [nStrLength + 1];
*pStrWord = '\0';
*pStrFinal = '\0';
nWordIndex = 0;

for (nIndex = 0;nIndex < nStrLength; nIndex++)
{

ch = m_strInput.GetAt(nIndex);
if ( ch != ' ' || nIndex == nStrLength )
{
pStrWord[nWordIndex] = m_strInput.GetAt(nIndex);
nWordIndex++;
}

if ( ch == ' ' )
{
pStrWord[nWordIndex++] = ' ';
pStrWord[nWordIndex] = '\0';
_tcscat(pStrFinal,_tcsrev(pStrWord));
nWordIndex=0;
}

if ( nIndex == (nStrLength - 1) )
{
pStrWord[nWordIndex++] = ' ';
pStrWord[nWordIndex] = '\0';
_tcscat(pStrFinal,_tcsrev(pStrWord));
nWordIndex = 0;
}
}
pStrFinal = _tcsrev(pStrFinal);
pStrFinal[nStrLength] = '\0';
m_strOutput = pStrFinal;
UpdateData(FALSE);

delete [] pStrWord;
delete [] pStrFinal;
}

I get error when deleting pStrFinal could anyone tell me why this happens. can any one of you explain me how to dump memory and to verify it.

Stephane Rodriguez.8-May-03 1:31

Stephane Rodriguez.

8-May-03 1:31

With pStrFinal = _tcsrev(pStrFinal);, you are messing your pointer away.
I recommend to use the MFC CString class instead (since you said it's a MFC dialog). This hides all this memory allocation mess.

Hari Krishnan (Noida)8-May-03 2:47

8-May-03 2:47

Hi,
Regarding the technique of dumping in-memory statistics, is
given below

Note: memstate1 takes snapshot of pre-memory leak and
memstate2 takes snapshot of post-memory leak. finally,
memstate3 makes the statistics based on both the snapshots.

CMemoryState memState1, memState2, memState3;

void CHello::MakeMemoryLeak()
{
memState1.Checkpoint();
LPCTSTR strMemoryLeak = new char[50];
memState2.Checkpoint();

memState3.Difference(memState1, memState2);
memState3.DumpStatistics();
}

Hope this Helps
Regards
~Hari~

David Crow8-May-03 3:14

David Crow

8-May-03 3:14

saravanaram wrote:
I get error when deleting pStrFinal...

So what's the error?

I suspect the problem lies within the following line, but can't know for sure without stepping through the code.

pStrFinal = _tcsrev(pStrFinal);

Hari Krishnan (Noida)8-May-03 4:13

8-May-03 4:13

Hi David,
if you see the memory contents of (pStrWord), it contains
5 (CD - valid memory allocated) and 4 FD(padded memory, # may differ)
(Note: Assume that nStrLength is 5)

Following code lines, are writing on unallocated memory.
pStrWord[nWordIndex++] = ' '; //This causes the problem.
pStrWord[nWordIndex] = '\0';
_tcscat(pStrFinal,_tcsrev(pStrWord));

as well,
pStrFinal = _tcsrev(pStrFinal); //This assignment also causes the problem.

Actually, he has to allocate the extra one byte of memory to put the space character (' ').

Hopefully, I am right.

regards
~Hari~