Question

I’d like to group elements by the first letter, but some different letters should be considered equal: A and Ä (and a and ä) should all be the same.

Source:

<root>
  <entry name="Aa" />
  <entry name="Ab" />
  <entry name="Äa" />
  <entry name="Ac" />
  <entry name="Ba" />
</root>

The transformation:

<xsl:stylesheet version="2.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
  <xsl:output indent="yes"/>

  <xsl:template match="root">
    <root>
      <xsl:for-each-group select="entry" group-by="upper-case(substring(@name,1,1))">
        <key><xsl:value-of select="current-grouping-key()"/></key>
      </xsl:for-each-group>
    </root>
  </xsl:template>

</xsl:stylesheet>

The result now:

<root>
   <key>A</key>
   <key>Ä</key>
   <key>B</key>
</root>

The result as I’d like it to have:

<root>
   <key>A</key>
   <key>B</key>
</root>

Where all entries except for “Bb” should be in the first group.

I assume the key to success is making the group-by() function correct to treat a,A,ä and Ä equal (this is true for some German sorting/ordering rules). But I have not found an xpath function that could handle that.

Answer 1

How about translate(substring(@name,1,1), 'Ä', 'A')?