Inferred Function Pointer Template Parameter - C / C++ / MFC Discussion Boards

Re: strcpy_s with WCHAR option

led mike24-Jun-09 11:55

led mike

24-Jun-09 11:55

Of course! Many developers just wave their magic ~~wand~~ keyboard at the problem. Laugh | :laugh:

VOID *function() help

Douglas Kirk24-Jun-09 7:35

Douglas Kirk

24-Jun-09 7:35

Hello I am working on some code and came across this

void *orpGetValue(char *key, SceSize *key_size)
{
void *value = NULL;
.....
.....
by using the void with the * infront of the name, the code will allow the passing of a pointer
that will allow the calling routine to assigned it to any variable type.

What is this called, I have been googling and can not find any info.
I know it is commonly used.

Thank you in advance.

Re: VOID *function() help

bulg24-Jun-09 7:45

bulg

24-Jun-09 7:45

a kludge

Re: VOID *function() help

Douglas Kirk24-Jun-09 7:49

Douglas Kirk

24-Jun-09 7:49

Does the * refer to it is a pointer to a VOID and that the return can be used to reference an int or a string?

I googled kludge, but didn't see any C references to it Smile | :)

Re: VOID *function() help

C^hris L^osinger24-Jun-09 9:04

C^hris L^osinger

24-Jun-09 9:04

it's sometimes called a "generic" pointer. the caller is expected to know what the pointer is really pointing to.

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Re: VOID *function() help

Douglas Kirk24-Jun-09 9:57

Douglas Kirk

24-Jun-09 9:57

Thank you!

I googled it and have found lots of info now. Smile | :)

Re: VOID *function() help

Stuart Dootson24-Jun-09 10:48

Stuart Dootson

24-Jun-09 10:48

I'd call it type-erasure really. You're removing all semblance of type information...

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Inferred Function Pointer Template Parameter

Skippums24-Jun-09 7:25

Skippums

24-Jun-09 7:25

I would like to create a template class that takes two template parameters:
1) A typename parameter, T
2) A pointer to a template function, F, that has the following declaration

template<typename U>
U DoSomething(int arg) { ... }

With such a declaration, I would like to instantiate my template class as follows:

MyTemplateClass<int, &DoSomething<SomeType>> myInstance;

Is there some way to declare MyTemplateClass such that I can infer the typename of SomeType? I have tried the following two cases but receive a compile error for both:

template<typename T, template <typename U> U (*F)(T)>
template<typename T, U (*F<typename U>)(T)>

I know that I could add a third template parameter, but would prefer to avoid it if at all possible. Thanks for any assistance,

Sounds like somebody's got a case of the Mondays

-Jeff

Re: Inferred Function Pointer Template Parameter

Stuart Dootson24-Jun-09 10:46

Stuart Dootson

24-Jun-09 10:46

No. DoSomething is not a type - it's a function. You're passing a value in, but for a class template, you need to have pre-declared those types.

Sorry and all that, but I don't think there's any way around it.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

CDialogTemplate

p_196024-Jun-09 7:14

p_1960

24-Jun-09 7:14

Hi,
when im trying to use...

CDialogTemplate dlt;
LPCTSTR ID=_T("IDD_TESTDLG_DIALOG");
if (!dlt.Load(ID)) return -1;

the issue is eventhough the ID is correct but the above if statement returns -1

but if i use
if (!dlt.Load(MAKEINTRESOURCE(CTestDlg::IDD))) return -1;
the above statement doesn"t return -1..

Please help me regarding the same...

Re: CDialogTemplate

David Crow24-Jun-09 8:22

David Crow

24-Jun-09 8:22

p_1960 wrote:
if (!dlt.Load(MAKEINTRESOURCE(CTestDlg::IDD))) return -1;

You might change this to:

LPTSTR ID2 = MAKEINTRESOURCE(CTestDlg::IDD);
if (! dlt.Load(ID2)) return -1;

and use the preprocessor's output to see if ID2 contains a different value that ID.

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Re: CDialogTemplate

siva45524-Jun-09 8:31

siva455

24-Jun-09 8:31

Thanks for ur Reply David ....

but the issue is with the below lines..

CDialogTemplate dlt;
LPCTSTR ID=_T("IDD_TESTDLG_DIALOG");
if (!dlt.Load(ID)) return -1;

the above code is returning -1 which is undesirable because ID is correct...

the issue is i have id as String like _T("IDD_TESTDLG_DIALOG")(ie im getting the ID of the resource as a String instead of CTestDlg::IDD) ...

Please correct me if im wrong....

Re: CDialogTemplate

David Crow24-Jun-09 8:35

David Crow

24-Jun-09 8:35

The point of the exercise was to compare the two (i.e., ID vs. ID2). MAKEINTRESOURCE() is a macro that the preprocessor will expand, which is why I suggested a temporary variable.

Re: CDialogTemplate

p_196024-Jun-09 8:48

p_1960

24-Jun-09 8:48

ya..but MAKEINTRESOURECE converts an integer value to a resource type ...

but in the case of

CDialogTemplate dlt;
LPCTSTR ID=_T("IDD_TESTDLG_DIALOG");
if (!dlt.Load(ID)) return -1;

i need to pass id as String instead of integer...the doubt it is not working is i send id as
string...

Sorry for inconvenience caused ....

Re: CDialogTemplate

David Crow24-Jun-09 8:56

David Crow

24-Jun-09 8:56

p_1960 wrote:
ya..but MAKEINTRESOURECE converts an integer value to a resource type ...

It returns a LPTSTR.

p_1960 wrote:
i need to pass id as String instead of integer...the doubt it is not working is i send id as
string...

Did you look at the preprocessor's output?

Re: CDialogTemplate

p_196024-Jun-09 9:03

p_1960

24-Jun-09 9:03

ya it"s not recognising the ID which sent as string but it is working fine if i pass ID AS
integer..
Pls let me know...

Re: CDialogTemplate

David Crow24-Jun-09 9:07

David Crow

24-Jun-09 9:07

p_1960 wrote:
ya...

So what is its output?

p_1960 wrote:
...it"s not recognising the ID which sent as string but it is working fine if i pass ID AS
integer..
Pls let me know...

You may want to re-read this thread to understand exactly what it is that I am asking of you.

Re: CDialogTemplate

Ozer Karaagac24-Jun-09 12:53

Ozer Karaagac

24-Jun-09 12:53

Dialog name IDs should be either a string or a 16-bit unsigned integer.

If you remove dialog id definition (#define IDD_TESTDLG_DIALOG number) from the file named "resource.h", it will work. Or you should enter that name with double quotes (like "IDD_TESTDLG_DIALOG") as dialog ID of dialog properties.

Best practice for include directives vs. settings search path ?

Maximilien24-Jun-09 4:27

Maximilien

24-Jun-09 4:27

Howdy, slow day today, waiting for a phone call.

I was looking at some code recently, and there was an include like this :

#include "myfile.h"

And I was wondering from what "library" this file comes from. I know I could do a right-click and open and look at the property... but from a code point of view it's not very practical (IMO).

So, I looked in the project's settings to see that there are about 25 lines of "additional include paths", one for each library we have:

for example :

../lib/lib1
../lib/lib2
../lib/lib3
../lib/lib4

So, the questions :

Is it best practice to limit the number of "additional include path" to a minimum and have more descriptive include directive in the code ?
for example :
in the project settings :

../lib

and in the code have this :

#include "lib1/myfile.h"
#include "lib2/myfile2.h"

Is there a compilation performance issue with having a large amount of include paths vs. having more descriptive
includes in the code ?

Any good reading about this topic available somewhere ?
Thanks.

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Re: Best practice for include directives vs. settings search path ?

Stuart Dootson24-Jun-09 7:12

Stuart Dootson

24-Jun-09 7:12

Maximilien wrote:
in the project settings :
../lib

and in the code have this :
#include "lib1/myfile.h"
#include "lib2/myfile2.h"

That's what I'd likely go for

Best practise? Is there one? I don't think so. But in the *nix world, they tend to use that pattern. For example, in my Mac's /usr/include directory, there are 267(!) directories for different libraries (like libxml, libxslt, rpc, subversion, python).

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Can we get column value from SQL (does not know member value)?

Curious 200924-Jun-09 4:22

Curious 2009

24-Jun-09 4:22

I would like to get all text values from my MS Access database, I can access directly each column value (ie: str[0] = FF_Text.m_Column1, str[1] = FF_Text.m_Column2, ...)

But instead do like that for 27 times ... I would like to access them through their columns! However, I could not find the way to retrieve column text value!

CString str[27];

strSQL.Format ("SELECT * FROM TABLE_Text WHERE Title = 'Information'");
FF_Text.Open (AFX_DAO_USE_DEFAULT_TYPE, strSQL, 0);
if (!FF_Text.IsEOF())
{
    for (i=0; i<27; i++)
    {	
        str[i] = FF_Text.(???)   // Get text value in intended column
    }
}
FF_Text.Close();

Can any one help?

Re: Can we get column value from SQL (does not know member value)?

David Crow24-Jun-09 5:05

David Crow

24-Jun-09 5:05

ATC2000 wrote:
str[i] = FF_Text.(???) // Get text value in intended column

Are you looking for the GetFieldValue() method?

Re: Can we get column value from SQL (does not know member value)?

Curious 200924-Jun-09 7:02

Curious 2009

24-Jun-09 7:02

I did try before but forgot to examine the error (not well define). Now it is OK, I got all column text!

Thanks for help Big Grin | :-D

IGPM interface

subhabasu24-Jun-09 2:51

subhabasu

24-Jun-09 2:51

Hi all,

I am trying to use the IGPM interface from the gpmgmt.dll. The dll is registered in Win2008 server. But when I execute my exe file (written in C++) it simply throws an HRESULT error - "0x80040154 The class is not regsiteresd" and the GetLastError returns "1008 ERROR_NO_TOKEN".

Any help is appriciated.

Thanks.

Subha

Close X button in tadded control and vertical scroll.

birajendu24-Jun-09 2:46

birajendu

24-Jun-09 2:46

Hi,
I created a tab control using Win32 , I require to add X button and h-scroll(Right top corner) as in VS2005 IDE. can any one give a idea how to Override tab control, X button like IE7 will also be good.

Thanks in advance.

Birajendu
SonicWALL
Bangalore
India

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