Re: [xsl] My Difficult counting problem

[Wendell Piez <wapiez at mulberrytech dot com>]

Tim,

This problem looks harder than it is. There are basically two things you 
need to solve it: (a) to restate the problem in a way more amenable to 
XSLT, and (b) apply a little fancy XPath (which you can learn by asking on 
this list :-).

You say "I don't know how loop through the nodes, and keep track of how many
occurrences there are up to the given position", which is basically about 
half right in the way of a solution. I say half since the XSL Way isn't to 
"loop through" anything, much less to keep track of anything while doing 
so. Yet the problem is easily solved if you just say "I want my output in 
the same order as my input [that's easy], and for each foo, I want my 
output to get a number reflecting how many foos of the same name came 
before it".

In XSLT this logic would be:

<xsl:template match="foo">
  <xsl:value-of 
select="count(preceding-sibling::foo[@name=current()/@name]) + 1"/>
</xsl:template>

Spiffed it up to get more exactly what you want:

<xsl:template match="myElement">
  <xsl:text>numberOccurrences[] = {</xsl:text>
  <xsl:apply-templates/>
  <xsl:text>};</xsl:text>
</xsl:template>

<xsl:template match="foo">
  <xsl:variable name="thisname" select="@name"/>
  <!-- this time we're using a variable just to make the logic a little 
clearer -->
  <xsl:if test="preceding-sibling::foo">
    <!-- we want a comma unless we're the first foo -->
    <xsl:text>, </xsl:text>
  </xsl:if>
  <xsl:value-of select="count(preceding-sibling::foo[@name=$thisname]) + 1"/>
  <!-- note we used the variable this time instead of current()/@name -->
</xsl:template>

You could do the same thing in a single xsl:template if you used an 
xsl:for-each inside it for the "loop" (which isn't a loop) -- but it would 
do the same thing.

Cheers,
Wendell


At 05:48 PM 8/22/2002, you wrote:
> hello,
>
> I need some help doing the following, I can't seem to figure out how to do
> this in XSL
>
> I need to convert something like this
> <myElement>
>    <foo name="foobar1"/>
>    <foo name="foobar2"/>
>    <foo name="foobar1"/>
>    <foo name="foobar3"/>
>    <foo name="foobar1"/>
>    <foo name="foobar1"/>
>    <foo name="foobar3"/>
> </myElement>
>
> and the output after running it through the XSL would be
>
> numberOccurrences[] = {1, 1, 2, 1, 3, 4, 2};
>
> basically for each foo with a duplicate name you put the occurrence number
> of it in the array at the correct position.
>
> You see that foobar1 occurs 4 times,
> the 1st occurrence is at position 0, while 2nd occurrence is at position 2,
> 3rd at position 4, and 5th at position 5. etc.
>
> I don't know how loop through the nodes, and keep track of how many
> occurrences there are up to the given position.

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Wendell Piez                            mailto:wapiez@mulberrytech.com
Mulberry Technologies, Inc.                http://www.mulberrytech.com
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