Re: [xml] Retrieving boolean/number/string value from XPath objects

[Daniel Veillard <veillard redhat com>]

On Fri, May 11, 2001 at 02:59:57PM +0200, Thomas Broyer wrote:
> Hi,
> Today I started implementing EXSLT's extensions (http://exslt.org) and I

  Good idea ! I kept the URL around but since I didn't finished the 
extension API, I decided to postpone. getting this contribution would
indeed be very cool :-)

> came to a reflexion I already had last fall while we were talking about
> libxslt.
>
> Why isn't there "basic" functions to convert values to
> number/boolean/string?

  Probably because I never took the time to do refectoring, and also
probably because I usually do most of those "in-situ" in the allocated
XPath object being passed (this is the case I think for the most simple
XPath casts).

> I'm convinced there should be functions or macros to:
>  · convert a "basic" value (xmlChar*, double, int, xmlXPathNodeSet) to
>    another one (xmlChar*, double, int)
>  · convert an XPath object to a "basic" type (xmlChar*, double, int)
> and I can't understand why there aren't yet.
> This would simplify other functions like sum() or even id() (and document()
> in libxslt) and avoid useless allocations/deallocations in many programs
> based on libxml or extension functions.
>
> The current functions for casting XPath objects to XPath objects should
> rely on these "low-level" functions.
>
> The basic idea is to work on xmlXPathObject's only at the beginning (when
> you receive arguments) and end (when you return values) of functions to
> avoid allocations/deallocations and not-instinctive manipulation of
> xmlXPathObject's.

  Yes there is definitively a lot of places in the XPath library where
allocations are far from optimal !

> Should I go for it or you disagree with such a refactoring?

  No it's a good idea, try to preserve the semantic of the existing
operation (including numbers ones ;-)

Daniel

-- 
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