Re: [xml] Question regarding XPath

["James Dennett" <jdennett technocom-wireless com>]

Daniel Veillard wrote:

> On Fri, Mar 16, 2007 at 09:03:01AM -0500, Ethan Metsger wrote:

[snip]

> > shed some light on how xmlXPathEval differs from
xmlXPathEvalExpression,
> > and whether the issue is related to the context passed?

This seems to be something of an FAQ around here.  It would be useful
for the documentation of these functions to document how they differ,
possibly with a reference to the XPath spec.  Maybe some kind soul
reading this thread can find the time to prepare a patch.  I don't have
time right now.
 
>   Use xmlXPathEval(), see XPath spec to see the real difference:
>   http://www.w3.org/TR/xpath#NT-LocationPath
>   [1]         LocationPath
>
>   http://www.w3.org/TR/xpath#NT-Expr
>   [14]        Expr

So the difference is that xmlXPathEvalExpression handles an XPath
"Expr", whereas xmlXPathEval handles an XPath "Location Path", which is
a particular kind of Expr.  In other words: xmlXPathEvalExpression
should be able to handle any expression that xmlXPathEval can, and a
number more.

(In http://mail.gnome.org/archives/xml/2001-July/msg00102.html you
appeared to agree with Wai-Sun Chia that they are functionally
identical.)

Is there a reason for advocating using the function that is documented
as less powerful?  Certainly in the code I have that uses libxml2, I
want to be able to evaluate any Expr, not only LocationPath expressions.

-- James