Subject: Re: [xsl] Re: Re: Node Selection From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Fri, 15 Jun 2001 12:13:41 -0700 (PDT) |
Hi Jeni, Moving from O(N*Log2(N)) to just O(N)is a great step forward. Now I understand that you didn't offer this solution, because someone had just said he "i felt afraid, when i saw jeni's example"... So, the next step will make your solution also look quite simple -- and you know what this step is -- stop writing customised max() templates on every occasion and use just one generic max() template. I'm just quoting one of your messages, with small adjustments: <date-timeMax:max /> <xsl:template match="/"> <xsl:text>Maximum value is: </xsl:text> <xsl:apply-templates select="document('')/*/date-timeMax:max)" > <xsl:with-param name="nodeset" select="//Activity"/> </xsl:apply-templates> </xsl:template> <xsl:template match="date-timeMax:max"> <xsl:param name="nodes" select="/.."/> <xsl:param name="n1" select="/.."/> <xsl:param name="n2" select="/.."/> <xsl:value-of select="concat($n1/Date, $n1/Time) > concat($n1/Date, $n1/Time) " /> </xsl:template> Cheers, Dimitre Novatchev. --- Jeni Tennison <mail@xxxxxxxxxxxxxxxx> wrote: > Dimitre Novatchev wrote: > >> > I am using Xalan for xsl transformations. I have some xml with > >> > multiple <Activity> nodes in it for each part that is processed. The > >> > activity nodes are not sorted in any way in the xml. I want to > >> > select only the latest activity (by Date, Time) to process in the > >> > transform for my output to show the last activity scan on this part > >> > and ignore all other activity scans. > >> > >> The easiest way to do this is to sort the Activity elements by their > >> Date and Time (in descending order), and then choose the first one > >> only to go on and process: > [snip] > > > > This is one of the most inefficient ways to find a maximum and Jeni > > must know it. In case there are thousands of nodes to be sorted, the > > unnecessary wait will be due exactly to following such an advice. > > Well I did say *easiest* rather than *most efficient* ;) > > Jim, if you have lots of Activity elements and find that your > transformation is unacceptably slow, then you could alternatively > use a recursive template. This finds the next following Activity that > occurs after this one, and if there is one then applies templates to > it in 'latest' mode, and so on recursively through the Activity > elements. If there isn't one, it applies templates to the Activity so > you can go on and process it. > > <xsl:template match="Activity" mode="latest"> > <xsl:variable name="date-time" select="concat(Date, Time)" /> > <xsl:variable name="next" > select="following-sibling::Activity > [concat(Date, Time) > $date-time][1]" /> > <xsl:choose> > <xsl:when test="$next"> > <xsl:apply-templates select="$next" mode="latest" /> > </xsl:when> > <xsl:otherwise> > <xsl:apply-templates select="." /> > </xsl:otherwise> > </xsl:choose> > </xsl:template> > > To kick this process off, you need to apply templates to the first > Activity element in your Part, in 'latest' mode: > > <xsl:template match="Part"> > <xsl:apply-templates select="Activity[1]" mode="latest" /> > </xsl:template> > > [Caveat: this template will involve very deep recursion, which might > still be a problem on some processors (including Xalan, I believe), if > you're unlucky with the ordering of your Activity elements. It also > assumes that processors are smart enough to optimise XPath expressions > that end in a [1] predicate, and to therefore stop when they find the > first node in the path, but that shouldn't be a problem in Xalan.] > > Cheers, > > Jeni > > --- > Jeni Tennison > http://www.jenitennison.com/ > > __________________________________________________ Do You Yahoo!? Spot the hottest trends in music, movies, and more. http://buzz.yahoo.com/ XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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