Re: [xml] Question regarding XPath



On Fri, Mar 16, 2007 at 09:39:33AM -0700, James Dennett wrote:
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.

  Actually no, they both call xmlXPathEvalExpr() and hence both evaluate
based on production 14. As I said there should be no perceived differences
between both call.

Daniel

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Daniel Veillard      | virtualization library  http://libvirt.org/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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