xpath - XSLT 2.0: How to replace() part of an element's value and use the result in a select operation? -

i've done bit of xpath in c++ , c# applications, first time using directly in xslt. have xml file formatted this:

<toplevel>   <foo>     <bar>prefix1_taxi</bar>     ...   </foo>   <foo>     <bar>prefix1_schoolbus</bar>     ...   </foo>   ...   <foo>     <bar>prefix2_taxi</bar>     ...   </foo>   <foo>     <bar>prefix2_schoolbus</bar>     ...   </foo> </toplevel> 

first, want select <foo> elements have <bar> element starts "prefix1_." appears work:

<xsl:for-each select="foo[bar[starts-with(., 'prefix1_')]]">     <!-- style , format values child elements of "prefix1_" <foo> -->  </xsl:for-each> 

from inside for-each block, want select <foo> element contains corresponding "prefix2_" element. want pull data out of each see fit.

for example, when for-each has selected "prefix1_taxi", want select foo element contains "prefix2_taxi" bar element.

<xsl:for-each select="foo[bar[starts-with(., 'prefix1_')]]">     <!-- retrieve corresponding "prefix2_" foo -->    <!-- style , format values child elements of "prefix1_" <foo> -->    <!-- style , format values child elements of "prefix2_" <foo> -->  </xsl:for-each> 

unfortunately, have no idea how go this. in traditional program following pseudocode:

string buf = barelement.name.replace("prefix1_", string.empty); xmlnode otherfoo = document.selectsinglenode("foo[bar[" + buf + "]]"); 

however xslt works different paradigm retrieving values , manipulating data, i'm trying break out of old mode of thinking.

using i've gathered googling on xslt, came pretty ugly:

1. select foo element containing bar starts text:

   foo[bar[starts-with(., ...)

2. replace "prefix1_" in our current <bar> element:

   replace(<xsl:value-of select='bar'/>, 'prefix1_', '')

this yields pretty ugly mess:

<xsl:value-of select="foo[bar[starts-with(., replace(<xsl:value-of select='bar'/>, 'prefix1_', ''))]]" /> 

i'm pretty sure <xsl:value-of> element isn't correct.

how go this? suspect i'm missing core concepts of how express concept in xslt. i'm slogging through w3.org page on xslt still need much more study , practice.

this xsl stylesheet should give flexibility foo elements contain "prefix2".

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/xsl/transform">   <xsl:output method="xml" indent="yes" omit-xml-declaration="yes"/>   <xsl:strip-space elements="*"/>    <!-- matches top level element , selects children prefix1 text. -->   <xsl:template match="toplevel">     <xsl:copy>       <xsl:apply-templates select="foo[bar[starts-with(., 'prefix1_')]]"/>     </xsl:copy>   </xsl:template>    <!-- we're @ foo element prefix1 text. select siblings of         same vehicle type, prefix2 text. -->   <xsl:template match="foo[bar[starts-with(., 'prefix1_')]]">     <xsl:variable name="vehicle" select="substring-after(bar, 'prefix1_')"/>     <xsl:apply-templates select="../foo[bar = concat('prefix2_', $vehicle)]"/>   </xsl:template>    <!-- in template, can whatever want foo element containing        prefix2 vehicles. example copies element , children. -->   <xsl:template match="foo[bar[starts-with(., 'prefix2_')]]">     <xsl:copy-of select="."/>   </xsl:template> </xsl:stylesheet>