C / C++ / MFC Discussion Boards

1-Jul-01 23:47

Hi everybody.

I have the following question. Is it possible to get behavour like this from templates.

template < typename T >
class TType
{
public:
CString GetAsString( )
{
CString sValue;

sValue.Format( GetFormat<t>( ), m_tValue );

return sValue;
}

protected:
T m_tValue;
};

Define some function that depended of the type will return different string for formating.

template < class int >
CString GetFormat( )
{
return "%d";
}

template < class float >
CString GetFormat( )
{
return "%.4f";
}

and then when this is used
TType< int > a; // will use template function for int

TType< float > a; // will use template function for float

Re: Template Question

Martin Vladic2-Jul-01 0:26

Martin Vladic

2-Jul-01 0:26

It is invalid C++. Your idea written correctly looks like this:

template <typename t="">
class TType
{
public:
CString GetAsString()
{
CString sValue;
sValue.Format(GetFormat<t>(), m_tValue);
return sValue;
}
protected:
T m_tValue;
};

template <class t=""> CString GetFormat();
template <> CString GetFormat<int>() { return "%d"; }
template <> CString GetFormat<float>() { return "%.4f"; }

Unfortunately, this doesn't work on VC++ 6.0 (GetFormat<int> is called even for float's).

Try this:

template <typename t="">
class TType
{
public:
TType(const T& value)
: m_tValue(value)
{
}

CString GetAsString()
{
CString sValue;
sValue.Format(TypeHelper<t>::GetFormat(), m_tValue);
return sValue;
}

protected:
T m_tValue;
};

template <class t=""> class TypeHelper;

template <> class TypeHelper<int>
{
public:
static CString GetFormat() { return "%d"; }
};

template <> class TypeHelper<float>
{
public:
static CString GetFormat() { return "%.4f"; }
};

--
Martin

Re: Template Question

2-Jul-01 0:41

Are you sure that this will work ?

Re: Template Question

Martin Vladic2-Jul-01 23:30

Martin Vladic

2-Jul-01 23:30

Hm, it seems that discussion boards software stripped some chars from my post. For example, in template specialization definition:

template <> class TypeHelper<int>

, it stripped "<int>" after class name.

Please send me request email, and I will send you correct version of my post.

Regards

--
Martin

Re: Template Question

Martin Vladic2-Jul-01 23:44

Martin Vladic

2-Jul-01 23:44

I found out why some chars was stripped from my message and how to send it correctly. So, here it is, again:

It is invalid C++. Your idea written correctly looks like this:

template
class TType
{
public:
CString GetAsString()
{
CString sValue;
sValue.Format(GetFormat(), m_tValue);
return sValue;
}
protected:
T m_tValue;
};

template <class T> CString GetFormat();
template <> CString GetFormat<int>() { return "%d"; }
template <> CString GetFormat<float>() { return "%.4f"; }

Unfortunately, this doesn't work on VC++ 6.0 (GetFormat<int> is called even for float's).

Try this:

template <class T>
class TType
{
public:
TType(const T& value)
: m_tValue(value)
{
}

CString GetAsString()
{
CString sValue;
sValue.Format(TypeHelper::GetFormat(), m_tValue);
return sValue;
}

protected:
T m_tValue;
};

template <class T> class TypeHelper;

template <> class TypeHelper<int>
{
public:
static CString GetFormat() { return "%d"; }
};

template <> class TypeHelper<float>
{
public:
static CString GetFormat() { return "%.4f"; }
};

--
Martin

Re: Template Question

Tomasz Sowinski2-Jul-01 1:12

Tomasz Sowinski

2-Jul-01 1:12

You need to create a GetFormat function template and specializations for different types. VC++ seems to have problems with some forms of specializations. I was able to make the following code work:

// in TType template
CString GetAsString()
{
CString sValue;
sValue.Format( GetFormat(m_tValue), m_tValue );
return sValue;
}

// without this specializations won't compile on VC 6
template < class T >
CString GetFormat(const T& unused)
{
return CString();
}

template < >
CString GetFormat(const float & unused)
{
	return "%.4e";
}

template < >
CString GetFormat(const int & unused)
{
	return "%d";
}

Tomasz Sowinski -- http://www.shooltz.com.pl

Displaying Graphical Primitives of RichText Format

1-Jul-01 23:26

Does anybody know a possibility to display graphical primitives as Rectangles,
that are saved in the RichTextFormat File through th CRichEdit Control or any
other control

eiselekd

Failure in CRecordSet::IsOpen()

Kristian Thelin1-Jul-01 23:09

Kristian Thelin

1-Jul-01 23:09

when i try to use CRecordSet functions such as SetAbsolutePosition and MoveNext etc, i get an error. When i debug, it complaints about the IsOpen function, that if m_hstmt is NULL, it returns FALSE. I can use the CRecordSet functions to a certain point, after that this error message keeps coming up.
Seems like my CRecordSet pointer looses it's position or something.
I'm using Visual Studio 6.0, and i'm trying to get information from an access database.

Confused | :confused:

Kristian

Re: Failure in CRecordSet::IsOpen()

olof neumann1-Jul-01 23:15

olof neumann

1-Jul-01 23:15

Hmmm. sounds tricky;P

...::: knowledge is king :::...

overriding CEDIT

1-Jul-01 21:43

I have a CEdit derived class. I wanted to override the OnChar messages and PreTranslateMessage. However, when I add these I get "member function not declared in CDerivedEdit" errors. I have checked that the correct entry is in the header file and the mapping macro in the implementation file. Am I doing something else wrong or is something weird somewhere?!

thanks in advance

WM_CLOSE

vijayaramaraju1-Jul-01 21:27

vijayaramaraju

1-Jul-01 21:27

I've been trying to close another application from within my application I've used EnumWindows to obtain the handle of the other application. The problem is If The Other Application Remains Active WM_CLOSE message works fine but if it is not active there goes the problem I'm unable to activate it and the Other Application remains without closing . Does anyone knows how to come over this? Confused | :confused:

Thanks in advance

P Vijaya Rama Raju

Re: WM_CLOSE

Gert Boddaert2-Jul-01 4:48

Gert Boddaert

2-Jul-01 4:48

Try sending WM_QUIT to the UI Thread.

--------------------------------------------------
If my messages appear curt, I apologize.
I try to be brief to save your time as well as mine.
--------------------------------------------------

Re: WM_CLOSE

Hadi Rezaee2-Jul-01 8:29

Hadi Rezaee

2-Jul-01 8:29

Can you write code ?

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

Re: WM_CLOSE

Jack Handy2-Jul-01 9:52

Jack Handy

2-Jul-01 9:52

Have you tried TerminateProcess() ?

Here is a sample:

//you can get the pid with Process32First() and Process32Next()
int KillPid(DWORD pid) {
	HANDLE hPid = OpenProcess(0, FALSE, pid);
	if (hPid != NULL) {
		if (TerminateProcess(hPid, 0) == TRUE) {
			CloseHandle(hPid);
			return 0;
		} else {
			CloseHandle(hPid);
			return GetLastError();
		}
		CloseHandle(hPid);
	}
	return 1;
}<pre>

Re: WM_CLOSE

Hadi Rezaee2-Jul-01 10:40

Hadi Rezaee

2-Jul-01 10:40

Thanks, it is useful example ...

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

Re: WM_CLOSE

Gert Boddaert2-Jul-01 21:36

Gert Boddaert

2-Jul-01 21:36

Some people say I can, most say I can't Big Grin | :-D

Try:
http://www.codeproject.com/threads/interprocesssync.asp

--------------------------------------------------
If my messages appear curt, I apologize.
I try to be brief to save your time as well as mine.
--------------------------------------------------

new & modal ... stupid questions ?

1-Jul-01 17:21

can you point me the difference beetween:

Option m_Option;
m_Option.DoModal();
and:
m_Option = new Option(this);
m_Option->DoModal();

Both work but what is the difference "new" create a new instance ?
but if I "new" something I assume I should delete it somewhere ?
I'm a bit lost here while MFC do so much things automaticly
I don't want to miss something and to get memory leak.

Thanks

Re: new & modal ... stupid questions ?

Christian Graus1-Jul-01 18:15

Christian Graus

1-Jul-01 18:15

The difference is that m_Option is obviously a member variable to a pointer, Option is just an istance of the dialog. You never call delete on a CWnd, you call DestroyWindow, which ( I believe ) will be called for you in the case of a modal dialog. You should definately set m_Option to NULL after the DoModal though, and also in your constructor, for safety.

Christian

#include "std_disclaimer.h"

People who love sausage and respect the law should never watch either one being made.

The things that come to those who wait are usually the things left by those who got there first.

Re: new & modal ... stupid questions ?

zhenguri1-Jul-01 19:10

zhenguri

1-Jul-01 19:10

In your option 's ::PostNcDestroy()
add :
delete this;
no memory leak;

Re: new & modal ... stupid questions ?

2-Jul-01 10:33

Thanks

"No Disk" message.

Gunter Maywald1-Jul-01 17:04

Gunter Maywald

1-Jul-01 17:04

I hope somebody can help me with this (before I tear all my hair out and/or reformat my disk and reinstall everything) Confused | :confused:

For the last week or so, every now and then, as I am working in Visual Studio, I get a dialog labelled "MSDEV.EXE - No Disk", with the message "There is no disk in the drive. Please insert a disk into drive \Device\Harddisk1\DR2.". Three buttons, labelled "Ok", "Cancel" and "Try Again" each seem to do nothing, I need to terminate Visual Studio via the Task Manager to clear the message. Sometimes there is a considerable time (Hours) between stating Visual Studio and when this happens, other times it may only be a few minutes. I have uninstalled and reinstalled Visual Studio to no avail. I would suspect the hardware, except that no other application is failing in any way! BTW, I am running Windows 2000 Professional, on a new computer. I never had a problem like this on my previous machine.
Regards,
Gunter

Gunter F. Maywald
CSIRO Entomology
Long Pocket Labs, Brisbane
Australia

Re: "No Disk" message.

Andrew Lawrence9-Feb-10 12:10

Andrew Lawrence

9-Feb-10 12:10

In Tools -> Options, you can go to the Directories tab and see where it's looking for things. If there are duplicate paths that don't exist anymore then you can just delete them from there and you'll have no problem anymore.

Converting CString to int in Visaul C++, please help.

JavaTony1-Jul-01 16:55

JavaTony

1-Jul-01 16:55

Hi,
I have two variables with types CString and int.

int nWidth;
CString strWidth;
strWidth = "110";

How do I convert strWidth("110") to int type(110) so I can store it in nWidth?
Please show me how to do this, thank you very much. Smile | :)

Re: Converting CString to int in Visaul C++, please help.

Matt Gullett1-Jul-01 16:58

Matt Gullett

1-Jul-01 16:58

use the atoi or atol functions.

iWidth = atoi(strWidth);

Re: Converting CString to int in Visaul C++, please help.

Stephen Kellett2-Jul-01 4:48

Stephen Kellett

2-Jul-01 4:48

Or you could use strtod() and strtol().

strtol() is useful if you want to read a number that is not in base 10. For example
to read hex numbers use strtol("0x12345678", NULL, 16)

_tcstol() and _tcstod() are the macros for UNICODE/MBCS portability

Stephen Kellett
--
C++/Java/Win NT/Unix variants
Memory leaks/corruptions/performance/system problems. UK based.
Problems with RSI/WRULD? Contact me for advice.

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