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Re: Problem with selecting UNIQUE attribute
- To: kevin at synergysa dot com dot au
- Subject: [xsl] Re: Problem with selecting UNIQUE attribute
- From: Dimitre Novatchev <dnovatchev at yahoo dot com>
- Date: Sun, 17 Jun 2001 03:52:44 -0700 (PDT)
- Cc: xsl-list at lists dot mulberrytech dot com
- Reply-To: xsl-list at lists dot mulberrytech dot com
Kevin Read wrote:
>
> It seems that no matter what combination of select expressions I use on the
> build-dirlist I am unable to select on the unique values. :-(
[snip]
>
> <xsl:template name="build-dirlist">
> <xsl:param name="LVL"/>
> <xsl:for-each select="//dir[@level=$LVL and not(preceding::parameter[@name
> = @name])]">
> <xsl:sort select="@name" order="ascending" />
> <option>
> <xsl:value-of select="@name"/>
> </option>
> </xsl:for-each>
> </xsl:template>
Hi Kevin,
The problem is in the following two lines of your code:
> <xsl:for-each select="//dir[@level=$LVL and not(preceding::parameter[@name
> = @name])]">
What you want is to get all "dir" elements on a level, such that their "name"
attribute is not equal to the "name" attribute of any of the preceding ***dir***
elements.
This can be specified as:
//dir[@level=$LVL and not(@name = preceding::dir/@name)]
After this correction the template will be working correctly. Its code will be:
<xsl:template name="build-dirlist">
<xsl:param name="LVL"/>
<xsl:for-each select="//dir[@level=$LVL and not(@name = preceding::dir/@name)]">
<xsl:sort select="@name" order="ascending" />
<option>
<xsl:value-of select="@name"/>
</option>
</xsl:for-each>
Cheers,
Dimitre Novatchev.
P.S. It is usually recommended to optimise expressions like "//dir" and also to use
the Muenchian method for grouping, which uses keys and can be much more efficient
than what you're using -- comparing every node with all preceding identically typed
nodes -- this has complexity of O(N*N), where N is the number of all nodes of this
same type in the xml source document.
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