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D - Static Virtual Member Functions

reply "anderson" <anderson firestar.com.au> writes:
Does D have Static Virtual Member Functions? It would be nice if it did. I
know and have used many workarounds in the past in C++ but they all have
drawbacks. If it doesn't, there's probably some good reason, so explain
that.
May 16 2002
parent reply "Pavel Minayev" <evilone omen.ru> writes:
"anderson" <anderson firestar.com.au> wrote in message
news:abvm8j$1iaj$1 digitaldaemon.com...

 Does D have Static Virtual Member Functions? It would be nice if it did. I

Could you please explain what are virtual (called via vtable) static functions for?
May 16 2002
next sibling parent reply "anderson" <anderson firestar.com.au> writes:
It's hard to think of an easy example (not that there aren't heaps of them).

In one case I need to register a list of classes as numbers, which made for
easy saving, and a host of other cool things. Perhaps you could suggest a
better way of doing this, but I still think static virtual member function
would be cool (and parhaps they're aready in D).

ie (C++ code)

//registers all classes with a private number
void registerElements()
{
 element * Temp;
 //Elements
 for (int n=1; n<getMaxElements(); n++)
 {
  //Create Element (won't be need if static virtual member functions were
supported)
  Temp = getElement(n);

  //If it exists
  if (Temp)
  {
   //Pass it's number
   Temp->setClassID(n);
   //Destroy Item
   delete Temp;
  }
 }
}

//Returns a new unit for the selected number
//Note, probably should make more generic
//When ever a new object needs to be defind, simply use getElement (parhaps
should be called newElement)
element * getElement(int Number)
{
 switch (Number)
 {
 case vertexEL::getClassID(): return new vertexEL();
 case lineEL::getClassID(): return new lineEL();
 default: return NULL;
 }
}

also the element extend this class

class IDClass
{
private:

public:
 IDClass();
 virtual ~IDClass();

 //Returns the very important Class ID.
 int getClassID();
 void setClassID(int ID);

 //Must be used in each sub class, returning a pointer to a static integer
value
 //More ugly c++ code to support static virtual member function
 virtual int * classIDPtr()=0;
};


The example above was for a drawing package, primitives where extended from
element. This allows for many comminalties to be definded once and used for
every class. Saving/undoing is a brezze and can be done in clusters. The
object could also define there own properties (dynamicly), but that's
another story.

This way programmers could work individually on the project, adding extended
classes into the program, test them and everything. Once the new class was
definded, it would be issued with a number (by the project's element number
keeper) and added to the main list of classes for that type (the above code
was modified slightly to support that). Admitly the register part in the
above code could be included as part of the static constructor code in D,
but if it was need to be dynamic... D would also improve apone many other
aspects of the code above (as I'm sure some of you will point out).

Using virtual static member functions would make the above example much
easier. There are documents on work arounds for static virtual member
functions for C++ (the above uses one of them), and I don't see why there
should be documents on workarounds, if it isn't a feature that should have
been included.

It would also be cool is static virtual properties (ie int) was supported.

I may be hard to imagine, but this way of coding has made multi-programming
much easier.

Thanks, for taking the time to read this long Doc.

"Pavel Minayev" <evilone omen.ru> wrote in message
news:abvt2u$1nut$1 digitaldaemon.com...
 "anderson" <anderson firestar.com.au> wrote in message
 news:abvm8j$1iaj$1 digitaldaemon.com...

 Does D have Static Virtual Member Functions? It would be nice if it did.


 Could you please explain what are virtual (called via vtable) static
 functions for?

May 16 2002
next sibling parent "anderson" <anderson firestar.com.au> writes:
I've made mistake in the previous code, should be,

element * getElement(int Number)
{
 switch (Number)
 {
 case 0: return new vertexEL();
 case 1: return new lineEL();
 default: return NULL;
 }
}

(I was thinking in curves  :) )

And just when the I-net disconnects. Grrrrrr

"anderson" <anderson firestar.com.au> wrote in message
news:ac02vo$1t98$1 digitaldaemon.com...
 It's hard to think of an easy example (not that there aren't heaps of

 In one case I need to register a list of classes as numbers, which made

 easy saving, and a host of other cool things. Perhaps you could suggest a
 better way of doing this, but I still think static virtual member function
 would be cool (and parhaps they're aready in D).

 ie (C++ code)

 //registers all classes with a private number
 void registerElements()
 {
  element * Temp;
  //Elements
  for (int n=1; n<getMaxElements(); n++)
  {
   //Create Element (won't be need if static virtual member functions were
 supported)
   Temp = getElement(n);

   //If it exists
   if (Temp)
   {
    //Pass it's number
    Temp->setClassID(n);
    //Destroy Item
    delete Temp;
   }
  }
 }

 //Returns a new unit for the selected number
 //Note, probably should make more generic
 //When ever a new object needs to be defind, simply use getElement

 should be called newElement)
 element * getElement(int Number)
 {
  switch (Number)
  {
  case vertexEL::getClassID(): return new vertexEL();
  case lineEL::getClassID(): return new lineEL();
  default: return NULL;
  }
 }

 also the element extend this class

 class IDClass
 {
 private:

 public:
  IDClass();
  virtual ~IDClass();

  //Returns the very important Class ID.
  int getClassID();
  void setClassID(int ID);

  //Must be used in each sub class, returning a pointer to a static integer
 value
  //More ugly c++ code to support static virtual member function
  virtual int * classIDPtr()=0;
 };


 The example above was for a drawing package, primitives where extended

 element. This allows for many comminalties to be definded once and used

 every class. Saving/undoing is a brezze and can be done in clusters. The
 object could also define there own properties (dynamicly), but that's
 another story.

 This way programmers could work individually on the project, adding

 classes into the program, test them and everything. Once the new class was
 definded, it would be issued with a number (by the project's element

 keeper) and added to the main list of classes for that type (the above

 was modified slightly to support that). Admitly the register part in the
 above code could be included as part of the static constructor code in D,
 but if it was need to be dynamic... D would also improve apone many other
 aspects of the code above (as I'm sure some of you will point out).

 Using virtual static member functions would make the above example much
 easier. There are documents on work arounds for static virtual member
 functions for C++ (the above uses one of them), and I don't see why there
 should be documents on workarounds, if it isn't a feature that should have
 been included.

 It would also be cool is static virtual properties (ie int) was supported.

 I may be hard to imagine, but this way of coding has made

 much easier.

 Thanks, for taking the time to read this long Doc.

 "Pavel Minayev" <evilone omen.ru> wrote in message
 news:abvt2u$1nut$1 digitaldaemon.com...
 "anderson" <anderson firestar.com.au> wrote in message
 news:abvm8j$1iaj$1 digitaldaemon.com...

 Does D have Static Virtual Member Functions? It would be nice if it



 I
 Could you please explain what are virtual (called via vtable) static
 functions for?


May 16 2002
prev sibling parent reply "Pavel Minayev" <evilone omen.ru> writes:
"anderson" <anderson firestar.com.au> wrote in message
news:ac02vo$1t98$1 digitaldaemon.com...
 It's hard to think of an easy example (not that there aren't heaps of

 In one case I need to register a list of classes as numbers, which made

 easy saving, and a host of other cool things. Perhaps you could suggest a
 better way of doing this, but I still think static virtual member function
 would be cool (and parhaps they're aready in D).

I see now. But I don't really see any other use for this but the creation of objects of class known only at run-time. If this is the case, we just need a built-in function, that'd take a ClassInfo, and return the new object of that class... I made this proposal lots of times already. This is what is usually called "virtual constructor".
May 16 2002
parent reply "anderson" <anderson firestar.com.au> writes:
There are such cases where "static virtual member functions" (or parhaps
"virtual static member functions" )  are need. You don't know how useful
they are until you use them. In something like D, I'd expect the virtual
part to be default as it is with other things.

Here's some else how had a simular problem,
http://cpptips.hyperformix.com/cpptips/virt_static_memb

"Pavel Minayev" <evilone omen.ru> wrote in message
news:ac0dov$26td$1 digitaldaemon.com...
 "anderson" <anderson firestar.com.au> wrote in message
 news:ac02vo$1t98$1 digitaldaemon.com...
 It's hard to think of an easy example (not that there aren't heaps of

 In one case I need to register a list of classes as numbers, which made

 easy saving, and a host of other cool things. Perhaps you could suggest


 better way of doing this, but I still think static virtual member


 would be cool (and parhaps they're aready in D).

I see now. But I don't really see any other use for this but the creation of objects of class known only at run-time. If this is the case, we just need a built-in function, that'd take a ClassInfo, and return the new object of that class... I made this proposal lots of times already. This is what is usually called "virtual constructor".

May 16 2002
parent "anderson" <anderson firestar.com.au> writes:
"anderson" <anderson firestar.com.au> wrote in message
news:ac1pk3$b76$1 digitaldaemon.com...
There are such cases where "static virtual member functions" (or parhaps
"virtual static member functions" )  are needed. You don't know how useful
they are until you've used them. In something like D, I'd expect the virtual
part to be default, as it is with other things.

(I seem to be missing droping alot of letters lately)

 Here's some else how had a simular problem,
 http://cpptips.hyperformix.com/cpptips/virt_static_memb

 "Pavel Minayev" <evilone omen.ru> wrote in message
 news:ac0dov$26td$1 digitaldaemon.com...
 "anderson" <anderson firestar.com.au> wrote in message
 news:ac02vo$1t98$1 digitaldaemon.com...
 It's hard to think of an easy example (not that there aren't heaps of

 In one case I need to register a list of classes as numbers, which



 for
 easy saving, and a host of other cool things. Perhaps you could



 a
 better way of doing this, but I still think static virtual member


 would be cool (and parhaps they're aready in D).

I see now. But I don't really see any other use for this but the creation of objects of class known only at run-time. If this is the case, we just need a built-in function, that'd take a ClassInfo, and return the new object of that class... I made this proposal lots of times already. This is what is usually called "virtual constructor".


May 16 2002
prev sibling parent "anderson" <anderson firestar.com.au> writes:
I've made mistake in the previous code, should be,

element * getElement(int Number)
{
 switch (Number)
 {
 case 0: return new vertexEL();
 case 1: return new lineEL();
 default: return NULL;
 }
}

(I was thinking in curves  :) )

And just when the I-net disconnects. Grrrrrr

"Pavel Minayev" <evilone omen.ru> wrote in message
news:abvt2u$1nut$1 digitaldaemon.com...
 "anderson" <anderson firestar.com.au> wrote in message
 news:abvm8j$1iaj$1 digitaldaemon.com...

 Does D have Static Virtual Member Functions? It would be nice if it did.


 Could you please explain what are virtual (called via vtable) static
 functions for?

May 16 2002