C / C++ / MFC

Re: Member Function Template [modified]

30-Jul-07 20:42

I have sound knowledge of Class Template & Function Template.
But I was trying to write a class as follows,

<br />
class CProg<br />
{<br />
	int val;<br />
public :<br />
	void SetVal(int y);<br />
	template<class T><br />
	void AddValues(T a, T b);<br />
};<br />
void CProg::SetVal(int y)<br />
{<br />
	val = y;<br />
}<br />
<br />
template<class T><br />
void CProg::AddValues(T a, T b)<br />
{<br />
T x = a+b;<br />
}<br />
<br />
void main()<br />
{<br />
	CProg prog;<br />
	prog.SetVal(9);<br />
}<br />

Above code works well. But when I change main(0 as follows,
void main()
{
CProg prog;
prog.SetVal(9);
int a,b;
a = b =8;
prog.AddValues(a,b);
}
It gives compile-time error as,
Failed to specialize function template 'void __thiscall CProg::AddValues(T,T)'
With the following template arguments:
'int'

Nelek30-Jul-07 20:54

30-Jul-07 20:54

If you dont make a return of your "T x" and you declare only "T a" and "T b" in your main... how can the programm do the operation? Try...

template
T CProg::AddValues(T a, T b)
{
T x = a+b;
return (T) x;
}

and...

void main()
{
CProg prog;
prog.SetVal(9);
int a,b, c;
a = b =8;
c = prog.AddValues(a,b);
}

What does now the programm say?

EDIT:

I have just realiced that the error you told has not much to do with my answer (but anyways is something it could fail). This code is from Simon Huge's template to a smart CList.

template<class TYPE, class ARG_TYPE>
inline CMyList<TYPE, ARG_TYPE> operator + (const CMyList<TYPE, ARG_TYPE> &lhs, const CMyList<TYPE, ARG_TYPE> &rhs)
{	CMyList newList(lhs);
	newList.AddTail(rhs);
	return newList;
}

Maybe it gives you an idea

-- modified at 3:00 Tuesday 31st July, 2007

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Andy Rama30-Jul-07 21:00

30-Jul-07 21:00

Thanks for your replay Nelek < Rose | [Rose]

>

But code given by you give same compile-time error.
Is there any another solution?

Andy Rama30-Jul-07 21:09

30-Jul-07 21:09

I didn't understand what you want to say.
Will you elobarate this?

Andy Rama30-Jul-07 21:22

30-Jul-07 21:22

As you have written member function as inline, i change code as following,

<br />
class CProg<br />
{<br />
	int val;<br />
public :<br />
	void SetVal(int y);<br />
	template<class T><br />
	void AddValues(T a, T b)<br />
	{<br />
	T x = a+b;<br />
	}<br />
};<br />
void CProg::SetVal(int y)<br />
{<br />
	val = y;<br />
}<br />
<br />
int main(int argc, char* argv[])<br />
{<br />
	CProg prog;<br />
	prog.SetVal(9);<br />
	int a,b;<br />
	a = b =8;<br />
	prog.AddValues(a,b);<br />
	double x, y<br />
	x = 12.1212;<br />
        y = 12.446;<br />
	prog.AddValues(x,y);<br />
	return 0;<br />
}

Above code is working properly. Thanks for that.

But eventhough, is there any other way for non-inline memeber function for class to use as Function Template ?

Nelek30-Jul-07 21:39

30-Jul-07 21:39

If it works... cool Poke tongue | ;-P

but actually... I edited the message because of the < class T >, I forgot the empty spaces so the web took them as format snippets.

Anyways... The inline statement is not needed. The only thing is that for so short functions is better because the compiler add the inline function wherever it is called, insteads of referencing and going to read the code everytime it is called.

It should work as well without the inline.

I'm glad helping Smile | :)

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

jhwurmbach30-Jul-07 22:10

jhwurmbach

30-Jul-07 22:10

Nelek wrote:
The inline statement is not needed. [...] It should work as well without the inline.

Probably not. The Compiler must see the definition of the template at every point where a new template is instantiated.
And as tou almost newer include CPP-files, the template body must be in the header.

Failure is not an option - it's built right in.

Nelek30-Jul-07 23:56

30-Jul-07 23:56

I didn't say "put the template in the .cpp". I said that the same template function should work as well defined as inline as not defined as inline. It is already clear that all template functions have to go in headers.

In my article the functions I added to the SmartList are not inline and works perfectly.

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Nelek30-Jul-07 21:12

Don't follow any man spiritually, don't do anything that will get you in sh*t if god is real - Bradml[^]

30-Jul-07 21:12

Try with...

template< class T >
class CProg
{
public :
int val;
void SetVal(int y);
void AddValues(T a, T b);
};

template< class T >
inline void CProg< class T >::SetVal(int y)
{
val = y;
}

template< class T >
inline T CProg< class T >::AddValues(T a, T b)
{
return (T) (a + b);
}

EDIT: Some corrections, like empty space between < > and class T, so the web doesn't take them as labels for format.

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

CString accumulation

tom groezer30-Jul-07 20:40

tom groezer

30-Jul-07 20:40

I'm having a Cstring buffer that I'm accumulating for n iterations. At the end of each iteration I add \r\n to the end of buffer. After end of all the iterations I'm writing the CString buffer to the CFile object. I'm seeing hre two things.

1) The characters occupy double space may be two bytes. So the look i expanded rather than the normal.

2) Instead of \r\n the file contains some junk square characters. Also the file is not written with full contents.

The project is build in VS2005 with unicode. IS it mandatory to build a project with the default unicode support in VS2005.

Re: CString accumulation

Rage30-Jul-07 20:59

Rage

30-Jul-07 20:59

1 is probably due to unicode. As for 2., post your writing code.

tom groezer wrote:
IS it mandatory to build a project with the default unicode support in VS2005

Not that I know of.

Re: CString accumulation

Joe Smith IX30-Jul-07 21:19

Joe Smith IX

30-Jul-07 21:19

tom groezer wrote:
IS it mandatory to build a project with the default unicode support in VS2005

I think it is not mandatory, but VS2005 default to UNICODE settings.

Regarding Interview

tasumisra30-Jul-07 20:26

tasumisra

30-Jul-07 20:26

Dear all,
Recently i have faced an interview .... so there the interviewer asked me.. have u knowledge of COM+ ... so what should i have to answer...

Now i am telling about me...

I am using the dlls(COM component) just for doing some logical operation from ASP page.or when i need the acess for the data base.. that time also from asp page only

so please tell me during interview what should i tell... about my work knowledge....

Tasu

Tasu

Re: Regarding Interview

mandanani30-Jul-07 20:31

mandanani

30-Jul-07 20:31

The more diplomatic answer is: I know the concepts but I have not used in realtime projects Laugh | :laugh:

Re: Regarding Interview

Nelek30-Jul-07 21:42