Hamish Mackenzie wrote:
>  On Thu, 2003-06-26 at 16:04, Stefan Seefeld wrote:
>  
> >I don't really understand why we need three different classes to
> >manage documents. In particular I don't understand why you provide
> >a 'document_ptr' that is a wrapper around document_ref.
>  
>  
>  The document_ref and document_ptr would only be used when a non owning
>  reference or pointer is required.  Even then you could use
>  dom::document * and dom::document & instead in most cases.
>  
>  One big difference between a reference and a pointer is that a reference
>  must contain a valid non null value.

ok, but are these types really needed ?

My current proposal only provides dom::document_ptr, and I use implicit
refcounting on the underlying document tree. It seems to work quite
fine. I provide a bool operator () that tells me whether the
document_ptr is referring to a document or not.


>  dom::document_ref doc1; // Error
>  dom::document_ref doc2( 0 ); // Error
>  dom::document_ptr doc3; // Ok
>  dom::document_ptr doc4( 0 ); // Ok
>  
>  This means you do not have to check references for null values.  A
>  pointer can be useful if you wish to be able to delay initialisation or
>  if an value is optional.
>  
>  void some_function( document_ref doc ); // You must pass a doc
>  void some_function( document_ptr doc ); // You could pass 0

ok, I can see that as useful.

> >And I don't use a 'document' class, as that is managed implicitely
> >by my dom::document_ptr:
> >
> >dom::document_ptr document; // create new document;
> >dom::document_ptr doc(document); // create second reference to it
> >dom::document_ptr doc2 = document.clone(); // clone it, i.e. make deep
> >                                               copy
>  
>  
>  This is not consistent with the standard library or C++ in general.  It
>  will seem strange that the pointer class
>  1) Does not require dereferencing

would you say the same if the class name was spelled 'document_ref'
instead ?

>  2) Contains a valid and non null value after default construction

right, see my followup post to that mail.

>  3) Has a constructor such as document_ptr( "config.xml" )
>  4) Has member functions such as write_to_file
>  
>  The alternative would allow both...
>  
>  boost::shared_ptr< dom::document > doc( new dom::document() );
>  boost::shared_ptr< dom::document > doc1( doc );
>  dom::document doc2( *doc1 );
>  
>  and if the 'doc1' reference was non-owning...
>  
>  dom::document doc();  // Create new doc
>  dom::document & doc1( doc ); // Second reference
>  dom::document doc2( doc1 );  // Deep copy

right, but given such an approach, what would nodes return in their
'parent()' method ?


Regards,
		Stefan

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