C / C++ / MFC

Numeric Template Error C2296

27-Jan-10 9:24

Well, that is rather a lot of questions to answer, however, I'll try.

Vaclav_Sal wrote:
I have a basic understanding about this macro __declspec(dllexport).

Knowledge of this is less important than understanding how a library (lib or dll) is linked to an executable. If you read the MSDN literature it should make this clearer.

Vaclav_Sal wrote:
However , there are lib and linker "options" __declspec(lib, "xx.lib") and __declspec(link, "xx.lib") which I do not understand.

The lib processor collects a set of object modules and builds a static (lib) or dynamic (dll) library. Generaly speaking Visual Studio or VC will set the correct options when you create the project. The linker options should be set when you select the lib file into your linker settings in the project options.

Vaclav_Sal wrote:
Also, the #include "library.h" is now in debug directory. I assume that I need a #ifdebug directive somewhere to keep the reference correct in release.

I'm not sure what you mean here, but I presume that this include should be added to your project whether debug or not, so you probably do not need any #ifdef.

Vaclav_Sal wrote:
Do I still need to register the DLL with windows (regsvr32) ?

I'm not sure about this, I just copy the dll to the Windows/System32 directory and my apps tend to work fine.

MVP 2010 - are they mad?

Skippums27-Jan-10 6:51

Skippums

27-Jan-10 6:51

I have a template that is to be used with numeric binary types, and takes the following form:

template<typename T>
inline T foo(T other) {
    if (std::numeric_limits<T>::is_integer) {
        T rval(5);
        rval |= other; // Error C2296: '|=' : illegal, left operand has type 'double'
        return rval;
    } else {
        return 5 * other;
    }
}

However, as noted in the comment, I get an error when calling the function with T == double. Is there some way to have such a method? I know two approaches that I could use, so I listed them with the associated reasons why I would like to not have to implement them.

Opt 1. Create template specializations for type float, double, and long double. The downside is that this prevents my method from being used in the future when/if the floating point types half (16-bits) or quad (128-bits) are implemented.
Opt 2. Create two different methods, fooInt and fooFloat, and force the user to notify me of the type being used. The only downside here is namespace clutter, so if there isn't some way of implementing foo as I have written it, this is the option I will choose.

Thanks for any assistance,

Sounds like somebody's got a case of the Mondays

-Jeff

Richard MacCutchan27-Jan-10 9:14

27-Jan-10 9:14

You have a problem between compile time checks and execution time checks. If you set T as double then the compiler will, correctly, give the Error C2296, even though your execution time code tries to check (incorrectly) whether the input is an integer; see here[^]. It is probably better to rethink what you are trying to do as the statement rval |= other; makes little sense whatever type T is.

MVP 2010 - are they mad?

Skippums27-Jan-10 10:15

Skippums

27-Jan-10 10:15

Thank you for your response. Yes, I understand why I am getting the error, as well as the fact that my checks are performed at runtime. My question is, is there some way to accomplish this without having to create a template specialization for every integer and floating point type? It seems absurd that there isn't some compile-time guard that I could use to perform the same logic, but I couldn't think of one specifically. Unless I hear any ideas on how to better accomplish this, I am planning to have one method for floating types and another for integer types. Thanks,

Sounds like somebody's got a case of the Mondays

-Jeff

Richard MacCutchan27-Jan-10 22:00

27-Jan-10 22:00

The issue to resolve, as I stated in my previous message, is the use of the |= operator. This makes no sense on a float or double operand and is thus rejected. If you really need this operator for some reason then you should cast the operand to an appropriate non-numeric type such as DWORD.

MVP 2010 - are they mad?

Skippums28-Jan-10 3:49

Skippums

28-Jan-10 3:49

OK... I must not be communicating clearly, so here is how I am currently interpreting your answers:

"There is no way to put a compile-time (ie, using the preprocessor) guard on a block of statements based on the type of a template parameter. If you want to execute code within a template for types with differing interfaces, you must either create specialized templates for each type, create multiple methods with unique signatures, or typecast the input to the appropriate type for each applicable section of code. Any of these methods will work, and there is no other way to accomplish the same thing."

Did I interpret your answers correctly, or is something above not true? Thanks,

Sounds like somebody's got a case of the Mondays

-Jeff

Richard MacCutchan28-Jan-10 5:16

28-Jan-10 5:16

Skippums wrote:
Did I interpret your answers correctly?

Well almost. All I am saying is that if you are using a template that specifies its type as float or double you must ensure that the following code does not violate any of the rules concerning that type. In your code you are using the |= operator on a value, which really has no meaning for numerics, particularly floating point numbers. All you need to do within your template code is use acceptable operators to manipulate your data, or cast the items to a 'logical' type; for example any of the mathematical operators (+ - * /) should work fine regardless of the type of the numbers.

MVP 2010 - are they mad?

Ken Moynihan28-Jun-10 16:41

Ken Moynihan

28-Jun-10 16:41

I'm having the same problem as Jeff.

Your answer that he is using the wrong operator misses the point.
I, for example, am trying to use the shift operators (<< or >>) in a numeric conversion.
The template also needs to take floats, and although I've used boost::is_integral to ensure that floats are not shifted, the compiler cannot see this runtime decision.

Richard MacCutchan28-Jun-10 21:29

28-Jun-10 21:29

Ken Moynihan wrote:
Your answer that he is using the wrong operator misses the point.

On the contrary, that is the point. If you wish to compile source code then that source must follow the rules of the language. If, at run time, you wish to overrirde or otherwise work around those rules by casting then you are free to do so.

It's time for a new signature.

kmoy00728-Jun-10 22:46

kmoy007

28-Jun-10 22:46

I think communication has broken down here.
Thank you for taking the time to reply anyway.

Richard MacCutchan29-Jun-10 1:40

scrolling image using GDI+ under Windows 7 is very slow and flicking

29-Jun-10 1:40

kmoy007 wrote:
I think communication has broken down here.

Obviously! Who are you and why are you responding?

It's time for a new signature.

CODEPC27-Jan-10 4:14

CODEPC

27-Jan-10 4:14

Hi,

My application is using GDI+ to handle image as a background. It works OK under Windows XP. I found recently that it display very slow under Windows 7.

// stretch the image to the target rectangle
Gdiplus::Graphics gr(dc);
gr.SetPageUnit(Gdiplus::UnitPixel);
gr.DrawImage(pBmp, x1, y1, abs(x2-x1), abs(y2-y1));

What kind problem it could be? How can I solve it?

Thank you very much,

Re: scrolling image using GDI+ under Windows 7 is very slow and flicking

LunaticFringe27-Jan-10 11:08

LunaticFringe

27-Jan-10 11:08

You might want to try updating your video board driver. Don't know for sure if it'll fix it, but this sounds like a typical driver issue.

L u n a t i c F r i n g e

Re: scrolling image using GDI+ under Windows 7 is very slow and flicking

CODEPC27-Jan-10 12:09

CODEPC

27-Jan-10 12:09

Hi,

I replaced video card and its driver. It did not improve any. There might something wrong with Windows 7.

Damn Windwos 7,

Thanks your reply.

Re: scrolling image using GDI+ under Windows 7 is very slow and flicking

LunaticFringe27-Jan-10 13:06

LunaticFringe

27-Jan-10 13:06

CODEPC wrote:
Damn Windwos 7

L u n a t i c F r i n g e

Closing a document and leaving the view

maycockt27-Jan-10 3:13

27-Jan-10 3:13

Hi,

Is there a way to close a document without closing the application?

What I mean by this using a menu option, e.g. File -> Close, to invoke a file save if need be, and then clearing the view, but not closing the application?

Obviously I can write a function that will do this for me, but is there a standard CDocument member that will do this for me?

TIA

Tony

Re: Closing a document and leaving the view [modified]

CPallini27-Jan-10 3:30

CPallini

27-Jan-10 3:30

I think you should override the OnCloseDocument method,...Well,...Good luck!
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.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

maycockt27-Jan-10 3:58

27-Jan-10 3:58

Hi,

Thanks for that.

I have managed to achieve what I wanted, except for 1 remaining item.

Having succssfully closed the document, and my View has reverted to the original empty View, I find that I can open new files, except for the one that was just closed. I cannot open the file that was previously open until I have viewed a different file.

Is there a flag I need to reset, or function call I need to make so it is possible to open the fiel immediately after it has been closed?

I've managed to overcome that problem now by using the DocTemplate and Removing the document, but I now find that if I use this method, wi have to close my application multiple times dependent on how many times I have closed a document, e.g. close 2 documents and I have to close the application twice (press the application 'X' button twice). Any suggestions?

TIA

Tony

modified on Wednesday, January 27, 2010 10:24 AM

krmed27-Jan-10 4:37

krmed

27-Jan-10 4:37

You didn't indicate if this is an MDI or SDI application, but either way there is a DeleteContents() method that's called automatically just before a document closes.

Perhaps that function may do what you need.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

maycockt27-Jan-10 4:48

27-Jan-10 4:48

Hi Karl,

It's a SDI.

I am using DeleteContents() as part of my closure code, see below.........

//if the data has been modified then save the file
if(TRUE == IsModified())
{
	OnFileSave();
}

//get the DocTemplate to enable document removal
CDocTemplate* pDocTemplate = GetDocTemplate();

if(NULL != pDocTemplate)
{
	pDocTemplate->RemoveDocument(this);
}

//delete the document content and revert the title to "Untitled"	
DeleteContents();
CString csUntitled;
csUntitled.LoadString(AFX_IDS_UNTITLED);
SetTitle(csUntitled);

//refresh the list view
UpdateAllViews(NULL);

AS I say, the only issue now is that I have to close mutliple times, once for each file opened.

Tony

krmed27-Jan-10 4:53

krmed

27-Jan-10 4:53

I'm not sure if it could be part of your problem, however it probably is not a good idea to call RemoveDocument. In an SDI, there is only one document, and it lasts for the life of the program - it's never destroyed.

Of course, your DeleteContents is also responsible for resetting any document member data to it's original state.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

maycockt27-Jan-10 4:58

27-Jan-10 4:58

Hi Karl,

If I remove the call to RemoveDocument, I'm left with not being able to reopen the last closed file - this is caused by the CDocTemplate::yesAlreadyOpen flag being set.
Is there a way to force this flag, or my DocTemplate, to be something that reflects that I have closed (hopefully!!) the last open file?

TIA

Tony

krmed27-Jan-10 5:05

krmed

27-Jan-10 5:05

Haven't tried it, but perhaps

CloseAllDocuments(FALSE)

will reset that flag. Check it out on MSDN[^]

In fact, calling CloseAllDocuments causes the call to DeleteContents.

Hope it helps.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

maycockt27-Jan-10 5:14