Re: [xml] Still some words about XPath

[Daniel Veillard <veillard redhat com>]

On Mon, May 14, 2001 at 07:55:33PM +0200, Thomas Broyer wrote:
> > >  · xmlXPathNewNodeSet returns an "empty node-set" object when it is
> > >    passed NULL, whereas xmlXPathNewNodeSetList returns NULL and
> > >    xmlXPathWrapNodeSet returns an empty object (obj->nodesetval is
> > >    NULL).
> > >    xmlXPathNewNodeSet is consistant with xmlXPathNewString and
> > >    xmlXPathNewCString.
>
> Actually, xmlXPathNewCString returns en empty object (stringval is NULL) if
> it is passed a NULL argument.
>
> >   Yes this makes sense, there is places where one want to create
> > the node set "before" for example before a loop without failing.
>
> So what should the "normal" behaviour be?

  if the constructor usues a input pointer, well if the pointer is NULL
make a minimalist allocation. For example it will allocate an empty 
node set.

> IMO the one of xmlXPathWrapNodeSet and xmlXPathNewCString to prevent
> useless allocations. stringval == NULL and stringval == "" should be
> considered equivalent (an empty string), idem for nodesetval == NULL and
> nodesetval->nodeTab == NULL.

  nodesetval == NULL and nodesetval->nodeTab == NULL are already equivalent.

This is a trade off:
  - doing an extra allocation
  vs
  - making a more complex/larger code (including on the client code)

In some cases it makes sense (i think it is for nodesets).

> I was thinking of xmlXPathConvertFunc, xmlXPathType, xmlXPathVariable,
> xmlXPathAxisFunc and xmlXPathAxis.
> There isn't any function using them, they are completely useless and
> unusable.

  Hum, those can disapear right ... They may have to be redefined 
with XML Query or XML Schemas reuse in XSLT-2.0.

Daniel

-- 
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