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Re: How smart are the XSLT processors? Are there any X

Subject: Re: How smart are the XSLT processors? Are there any XSLT processors that convert tree-recursive functions into efficient iterative procedures?
From: Dimitre Novatchev <dnovatchev@xxxxxxxxx>
Date: Wed, 28 Apr 2010 19:44:49 -0700
Re:  How smart are the XSLT processors? Are there any X
On Wed, Apr 28, 2010 at 7:17 PM, Markus Flatscher
<markus.flatscher@xxxxxxxxxxxx> wrote:
> Dear David,
> Can you quickly point me to somewhere (just a list thread or something)
> where your pet peeve about using xsl:variable with content is explained? At
> my current learning stage, that would be very helpful to me, especially
> since I do what I'm not supposed to do a lot, and I'd like to learn how to
> do it better. Also, other than reading (and understanding) the specs, is
> there any recommended reading you have for intermediate users of
> XPath/XQuery/XSLT2? Or should we just keep re-reading Mr. Michael Kay?

Re: the 2nd part of this question:

Here is a link to a SO question I answered recently:


Dimitre Novatchev
Truly great madness cannot be achieved without significant intelligence.
To invent, you need a good imagination and a pile of junk
Never fight an inanimate object
You've achieved success in your field when you don't know whether what
you're doing is work or play

> Thanks!
> Markus
> David Carlisle wrote:
>> On 28/04/2010 23:20, Florent Georges wrote:
>>> David Carlisle wrote:
>>> B  Hi,
>>>> You are making it pretty inefficient in any case by using
>>>> value-of (or relying on your xslt engine to optimise this away)
>>>> by using value-of you are asking for a document node with a
>>>> text node child
>>> B  I didn't follow the whole discussion in details, so I probably
>>> missed something, but why do you say "by using value-of you are
>>> asking for a document node"? B I thought it just created one text
>>> node.
>>> B  Regards,
>> er because it was the middle of the night and I'm so used to moaning at
>> people for using xsl:variable with content rather than a select attribute
>> that "document node with text node child" just slipped off my fingers,
>> sorry. (If you look at the saxon list you'll see that I hadn't woken up
>> enough this morning to notice my error:-)
>> but the main point is that it's really too hard to expect automatic
>> conversions from O(n^2) algorithms to O(log n). My own attempt was the
>> following which I'd hoped would beat dimitre's for speed, but it doesn't
>> consistently, and his has the advantage of using exact integer arithmetic
>> didn't do the analysis to see at what the point the following will succumb
>> to rounding error)
>> <xsl:function name="ex:pow" as="xs:decimal">
>> B  <xsl:param name="a" as="xs:decimal"/>
>> B  B <xsl:param name="n" as="xs:integer"/>
>> B  B <xsl:choose>
>> B  B  <xsl:when test="$n=0">
>> B  B  B <xsl:sequence select="1"/>
>> B  B  </xsl:when>
>> B  B  <xsl:when test="$n=1">
>> B  B  B <xsl:sequence select="$a"/>
>> B  B  </xsl:when>
>> B  B  <xsl:when test="$n mod 2 = 0">
>> B  B  B <xsl:sequence select="for $z in ex:pow($a,$n idiv 2) return
>> B  B  </xsl:when>
>> B  B  <xsl:otherwise>
>> B  B  B <xsl:sequence select="for $z in ex:pow($a,$n idiv 2) return
>> $z*$z*$a"/>
>> B  B  </xsl:otherwise>
>> B  B </xsl:choose>
>> </xsl:function>
>> <xsl:variable name="phi"
>> select="1.618033988749894848204586834365638117720"/>
>> <xsl:variable name="r5"
>> select="2.2360679774997896964091736687312762354406"/>
>> <xsl:function B name="ex:fibclosed" as="xs:integer">
>> B <xsl:param name="n" B as="xs:integer"/>
>> B <xsl:sequence select="xs:integer(floor(ex:pow($phi,$n) div $r5 +
>> </xsl:function>
> --
> Markus Flatscher, Project Editor
> ROTUNDA, The University of Virginia Press
> PO Box 801079, Charlottesville, VA 22904-4318 USA
> Courier: 310 Old Ivy Way, Suite 302, Charlottesville VA 22903
> Email: markus.flatscher@xxxxxxxxxxxx
> Web: http://rotunda.upress.virginia.edu/

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