Hi, Sam. Sam Prokop <spro...@4tek.de> wrote on 02/12/2010 08:53:39 AM: > <xsl:template match="/"> > <xsl:apply-templates select="//AAA/BBB"> > <xsl:sort select="CCC"/> > </xsl:apply-templates> > </xsl:template> > > <xsl:template match="BBB"> > <xsl:value-of select="CCC"/> = <xsl:value-of > select="preceding::CCC"/> : <xsl:value-of select="CCC = preceding::CCC"/><br/> > </xsl:template> > > Result: > A=:false > A=A:true > A=A:true > B=A:false > B=A:true > B=A:true > C=A:false > > Does the comparison “CCC = preceding::CCC” use the sorted Node-Set > for preceding and the select “preceding::CCC” use the document node set?
I think this has more to do with the differences in the meaning of the relational operators and of conversion to string than the effect of sorting. xsl:value-of converts the selected value to string and uses that string value to construct a new text node. That conversion is performed as if the XPath string function was applied to the value.[1] "A node-set is converted to a string by returning the string-value of the node in the node-set that is first in document order. If the node-set is empty, an empty string is returned." So when you write xsl:value-of select="preceding::CCC" that selects the all the CCC elements that precede the context node (the BBB element) in document order, and the conversion to string selects the first of those. So, except when the context node is the first BBB element which has no preceding CCC elements, the xsl:value-of is always getting the string value of the very first CCC node - that is, "A". From section 3.4 of XPath 1.0,[2] "If both objects to be compared are node-sets, then the comparison will be true if and only if there is a node in the first node-set and a node in the second node-set such that the result of performing the comparison on the string-values of the two nodes is true." So when you write, <xsl:value-of select="CCC = preceding::CCC"/>, that selects two sets of nodes: the CCC element children of the BBB element, and all the CCC elements that precede that BBB element in document order. Then, if there is node in the first set and a node in the second set whose string values are equal, the result of the comparison is true. When you come to the first BBB node that has a CCC child with string value "B", for instance, the result of the comparison will be false, but for all subsequent BBB elements with a CCC child with string value "B", the result of the comparison must be true. I hope that helps to clarify things. If you can describe what you're actually trying to do, somebody might be able to suggest how you could write that in XSLT. Thanks, Henry [1] http://www.w3.org/TR/xpath/#function-string [2] http://www.w3.org/TR/xpath/#booleans ------------------------------------------------------------------ Henry Zongaro XML Transformation & Query Development IBM Canada Lab T/L 313-6044; Phone +1 905 413-6044 mailto:zong...@ca.ibm.com
