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?
Thanks!
Markus
David Carlisle wrote:
On 28/04/2010 23:20, Florent Georges wrote:
David Carlisle wrote:
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
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"? I thought it just created one text
node.
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 (I 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">
<xsl:param name="a" as="xs:decimal"/>
<xsl:param name="n" as="xs:integer"/>
<xsl:choose>
<xsl:when test="$n=0">
<xsl:sequence select="1"/>
</xsl:when>
<xsl:when test="$n=1">
<xsl:sequence select="$a"/>
</xsl:when>
<xsl:when test="$n mod 2 = 0">
<xsl:sequence select="for $z in ex:pow($a,$n idiv 2) return
$z*$z"/>
</xsl:when>
<xsl:otherwise>
<xsl:sequence select="for $z in ex:pow($a,$n idiv 2) return
$z*$z*$a"/>
</xsl:otherwise>
</xsl:choose>
</xsl:function>
<xsl:variable name="phi"
select="1.618033988749894848204586834365638117720"/>
<xsl:variable name="r5"
select="2.2360679774997896964091736687312762354406"/>
<xsl:function name="ex:fibclosed" as="xs:integer">
<xsl:param name="n" as="xs:integer"/>
<xsl:sequence select="xs:integer(floor(ex:pow($phi,$n) div $r5 +
0.5))"/>
</xsl:function>
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