Re: [xsl] Finding triples with same/distinct attribute value

[Michael Kay <mike@xxxxxxxxxxxx>]

On 29/02/2012 20:26, Michael M|ller-Hillebrand wrote:
> Dear gurus,
>
> I have a solution but I am eager to learn whether there is a better method to solve the problem.
>
> There is a number of elements with an attribute. The task is to find every triple of elements with the same attribute value or with distinct attribute values. I solved it using xsl:for-each loops but feel like having missed some XPath 2 features. I am looking forward to your comments.
I think you need to state the requirement more clearly. 
Reverse-engineering it from your code isn't that easy. Is your 
definition of a "triple" this: "a sequence of three distinct <pot> 
elements, not necessarily adjacent, but in document order"?

Michael Kay
Saxonica
> - Michael
>
> PS: I get a result of 60 triples with the sample file.
>
> Input:
>
> <pots>
>   <pot a="3" />
>   <pot a="3" />
>   <pot a="3" />
>   <pot a="1" />
>   <pot a="1" />
>   <pot a="1" />
>   <pot a="1" />
>   <pot a="1" />
>   <pot a="1" />
>   <pot a="3" />
>   <pot a="2" />
>   <pot a="3" />
> </pots>
>
> XSL:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; version="2.0"
>   xmlns:xs="http://www.w3.org/2001/XMLSchema";
>   xmlns:my="http://my";
>   exclude-result-prefixes="xs my"
>   >
>   <xsl:output indent="yes"/>
>
>   <xsl:template match="pots">
>    <result>
>     <xsl:sequence select="my:triples(*)" />
>    </result>
>   </xsl:template>
>
>   <xsl:function name="my:triples" as="node()*">
>    <xsl:param name="nodes" as="node()+"/>
>
>    <!-- common values -->
>    <xsl:for-each select="$nodes">
>     <xsl:variable name="t1" select="."/>
>     <xsl:for-each select="$t1/following-sibling::*[@a eq $t1/@a]">
>      <xsl:variable name="t2" select="."/>
>      <xsl:for-each select="$t2/following-sibling::*[@a eq $t1/@a]">
>       <triple>
>        <xsl:value-of select="string-join((my:pos($nodes, $t1), my:pos($nodes, $t2), my:pos($nodes, .)), ' ')" />
>       </triple>
>      </xsl:for-each>
>     </xsl:for-each>
>    </xsl:for-each>
>
>    <!-- distinct values -->
>    <xsl:for-each select="$nodes">
>     <xsl:variable name="t1" select="."/>
>     <xsl:for-each select="$t1/following-sibling::*[@a ne $t1/@a]">
>      <xsl:variable name="t2" select="."/>
>      <xsl:for-each select="$t2/following-sibling::*[@a ne $t1/@a and @a ne $t2/@a]">
>       <triple>
>        <xsl:value-of select="string-join((my:pos($nodes, $t1), my:pos($nodes, $t2), my:pos($nodes, .)), ' ')" />
>       </triple>
>      </xsl:for-each>
>     </xsl:for-each>
>    </xsl:for-each>
>
>   </xsl:function>
>
>   <xsl:function name="my:pos" as="xs:string">
>    <xsl:param name="nodes" as="node()+"/>
>    <xsl:param name="node" as="node()"/>
>    <xsl:value-of select="count($nodes[$node>>  .]) + 1" />
>   </xsl:function>
>
> </xsl:transform>