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[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Selecting similar XML nodes by a sort criteria
 At 04:46 PM 10/4/2007, you wrote: Before that, the color has nothing to do with the areacode being even or odd. You didn't say that, and neither did your data, but it wasn't hard to guess. For example --> The next question is whether you can use a node-set() extension function. (This would depend on your processor and operational requirements, but you haven't said what processor you're using, so again we have to guess.) If you can, two passes on the data would make this easier, at any rate conceptually. Well, okay ... here's an adaptation of a grouping algorithm to handle it (no extensions necessary): Input: <pile> <item name="Albert" number="1"/> <item name="Berenice" number="4"/> <item name="Camille" number="4"/> <item name="Dora" number="2"/> <item name="Eustace" number="5"/> </pile> stylesheet: <xsl:key name="item-by-number" match="item" use="@number"/> <!-- allows us to select item elements in global scope by means of their @number --> <xsl:template match="pile"> <xsl:for-each select="item[generate-id()=generate-id(key('item-by-number',@number)[1])]"> <!-- iterating over each first item in the group of items with its number --> <xsl:sort select="@number"/> <!-- sorting by number --> <xsl:variable name="color"> <xsl:choose> <xsl:when test="position() mod 2">red</xsl:when> <!-- assigning color red to first items in odd position among first items --> <xsl:otherwise>green</xsl:otherwise> <!-- assigning green to the others --> </xsl:choose> </xsl:variable> <xsl:for-each select="key('item-by-number',@number)"> <!-- iterating over all the items with this @number --> <tr bgcolor="{$color}"> <td> <xsl:value-of select="@number"/> </td> <td> <xsl:value-of select="@name"/> </td> </tr> </xsl:for-each> </xsl:for-each> </xsl:template> This uses the standard XSLT 1.0 idiom to select a set of nodes representing a set of groups of nodes, by selecting the single node whose generated id is the same as the generated id of the first node in the group. A key is used to collect members of the group. Once we have this set (of first items in their groups), we can select it with a for-each, which also gives us a context size and context position for each -- the context position (returned by the position() function) of course alternates between odd and even. The technique is generally called "Muenchian grouping" after Steve Muench, who first applied a key to the problem (thereby optimizing its performance significantly), although it's probably safe to say that several different people contributed to its development. Oh -- output: <tr bgcolor="red"> <td>1</td> <td>Albert</td> </tr> <tr bgcolor="green"> <td>2</td> <td>Dora</td> </tr> <tr bgcolor="red"> <td>4</td> <td>Berenice</td> </tr> <tr bgcolor="red"> <td>4</td> <td>Camille</td> </tr> <tr bgcolor="green"> <td>5</td> <td>Eustace</td> </tr> I hope this helps, Wendell ====================================================================== Wendell Piez mailto:wapiez@xxxxxxxxxxxxxxxx Mulberry Technologies, Inc. http://www.mulberrytech.com 17 West Jefferson Street Direct Phone: 301/315-9635 Suite 207 Phone: 301/315-9631 Rockville, MD 20850 Fax: 301/315-8285 ---------------------------------------------------------------------- Mulberry Technologies: A Consultancy Specializing in SGML and XML ====================================================================== 
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