From: Hamish Mackenzie (hamish_at_[hidden])
Date: 2003-06-27 08:48:15
On Fri, 2003-06-27 at 12:53, Anthony Williams wrote:
> It was meant to be a description of semantics, in terms of a sample
> A node that is not part of a document is a free-standing subtree that needs
> adding to a document. If it is an element, then you can treat it as if it is
> the root node of a document. If it is anything else, then you are more limited
> in what you can do, but then what does it mean to perform an XPath query on a
> If the underlying API requires that the document is kept alive to keep the
> nodes alive, then the wrapper class must handle this, whilst simulating the
> above semantic description.
If you look in one of my other posts you will see a description of just
that. The thing that concerns me most about this is
doc.find( path ).parent(); // non null (unless it found the root node)
node n( doc.find( path ) );
n.parent(); // User may not expect this to be null
n.document(); // or this
You could have a node_container (or standalone_node) which had no parent
or document methods but otherwise looked like a node.
node_container n( doc.find( path ) );
n.parent(); // compile time error
n.document(); // compile time error
which is good but doesn't really solve the problem...
n.first_child().document(); // null
My preference is that if you want to make a copy of a node you have to
have a new document...
document doc2( doc.find( path ) );
doc2.root().parent(); // null but you would expect that (it's the root)
doc2.root().document(); // non null as you would expect
That way the user can rely on parent() to be non null for all but root
nodes and document() can return a reference since it can never be null.
> > You could copy the libxml2 tree into your own structure but then you are
> > on your own when it comes to higher level things like xpath and xslt.
> I imagined that you would write forwarding functions for the underlying API,
> so when you are given an Xpath query, you pass it on to the underlying API and
> then wrap the result.
Then you would need to keep libxml2 version of the tree too and
synchronise any changes (or rebuild it every time you want to call a
-- Hamish Mackenzie <hamish_at_[hidden]>
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk