typedef for template function

[Andrey Balaguta]

Hello, All!

I need to define new type for template function, but I've forgotten how to
use "template" in conjunction with "typedef" %) I've tried "typedef template
<class T> void (*TDataDestruct or) (T Data)" and "template <class T> typedef
void (*TDataDestruct or) (T Data)", both don't work with error "template must
be classes or functions" (bcc5.5). Point me to right answer :) Thanks in
advance

With best regards, Andrey Balaguta. E-mail: uj2@mail.ru

[Rob Williscroft]

Re: typedef for template function

Andrey Balaguta wrote in news:3fc0ff0e$1 @news.itcom.net .ua:
[color=blue]
> Hello, All!
>
> I need to define new type for template function, but I've forgotten
> how to use "template" in conjunction with "typedef" %) I've tried
> "typedef template <class T> void (*TDataDestruct or) (T Data)" and
> "template <class T> typedef void (*TDataDestruct or) (T Data)", both
> don't work with error "template must be classes or functions"
> (bcc5.5). Point me to right answer :) Thanks in advance
>[/color]

What you've fogotten is that you can't do it (unless you have a time
machinr that is :).

There are currently no such things as template typedef's in C++.

Perhapse you could say why you think you need them, there is most
probably an alternative.

Rob.
--

http://www.victim-prime.dsl.pipex.com/

[Andrey Balaguta]

Re: typedef for template function

Hello, Rob!
You wrote on 23 Nov 2003 19:05:19 GMT:

RW> What you've fogotten is that you can't do it (unless you have a time
RW> machinr that is :).


I think I did that some time ago, but I will not approve that :)


RW> Perhapse you could say why you think you need them, there is most
RW> probably an alternative.


I'm doing a balanced binary search tree (template-based). A node class has
an option to destruct children recursively (i.e. node destructor destructs
node's left and right children before die itself). So there is need to
destruct data automatically, which is kind of problem, because data may be a
pointer, so it must be deleted (automatically too). I've found only solution
is to set up addition variable (function pointer, that takes the only
parameter -- data) that destructs data (if it is null, node destructor
simply ignores data). Here is a chunk of code:

// here is a problem :)
template <class T>
typedef void (*TDataDestruct or) (T data);

// ......

template <class T>
class TBinTreeNode
{
public :
//.........
T Data;
TDataDestructor DataDestructor;
bool RecursiveDelete ;
// ....
~TBinTreeNode (void)
{
if (DataDestructor ) DataDestructor (Data);
if (RecursiveDelet e)
{
if (lnode) delete rnode;
if (rnode) delete lnode;
}
}
};


Any help appreciated, thanks :)

With best regards, Andrey Balaguta. E-mail: uj2@mail.ru

[Rob Williscroft]

Re: typedef for template function

Andrey Balaguta wrote in news:3fc10c61$1 @news.itcom.net .ua:
[color=blue]
> Hello, Rob!
> You wrote on 23 Nov 2003 19:05:19 GMT:
>
> RW> What you've fogotten is that you can't do it (unless you have a
> time machinr that is :).
>
>
> I think I did that some time ago, but I will not approve that :)
>
>
> RW> Perhapse you could say why you think you need them, there is most
> RW> probably an alternative.
>
>
> I'm doing a balanced binary search tree (template-based). A node class
> has an option to destruct children recursively (i.e. node destructor
> destructs node's left and right children before die itself). So there
> is need to destruct data automatically, which is kind of problem,
> because data may be a pointer, so it must be deleted (automatically
> too). I've found only solution is to set up addition variable
> (function pointer, that takes the only parameter -- data) that
> destructs data (if it is null, node destructor simply ignores data).
> Here is a chunk of code:
>
> // here is a problem :)
> template <class T>
> typedef void (*TDataDestruct or) (T data);
>
> // ......
>[/color]

/* do nothing default version
template < typename T >
inline void data_destuctor( T & )
{
}

/* Overload for pointer */
template < typename T >
inline void data_destuctor( T *data )
{
delete data;
}
[color=blue]
> template <class T>
> class TBinTreeNode
> {
> public :
> //.........
> T Data;[/color]

[snip]
[color=blue]
> bool RecursiveDelete ;
> // ....
> ~TBinTreeNode (void)
> {[/color]

[snip]
data_destuctor( Data );
[color=blue]
> if (RecursiveDelet e)
> {
> if (lnode) delete rnode;
> if (rnode) delete lnode;
> }
> }
> };
>[/color]

Rob.
--

http://www.victim-prime.dsl.pipex.com/