xslt transform list and take max - dictionary

Question

I want to:
select all attributes "foo", which are string values, and store the values in a list.
transform each value of attribute "foo" in this list using some map in my xslt to a number.
select the max value of the list and output that.
So given the following xml:
<t>
<tag foo="A">apples</tag>
<tag foo="C">oranges</tag>
<tag foo="B">trees</tag>
</t>
And the following mapping:
<xsl:variable name="myMap">
<entry key="A">1</entry>
<entry key="B">2</entry>
<entry key="C">3</entry>
</xsl:variable>
The output would be:
<max>3</max>
Another question, why can't I indent my code? I'm putting spaces but it's not working.

Answer 1

I This standard XSLT 1.0 transformation (most resembling your approach):
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:variable name="vrtfMap">
<entry key="A" value="1"/>
<entry key="B" value="2"/>
<entry key="C" value="3"/>
<entry key="X" value="8"/>
</xsl:variable>
<xsl:variable name="vMap" select=
"document('')/*/xsl:variable[#name = 'vrtfMap']/*"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="#foo">
<xsl:attribute name="foo">
<xsl:value-of select="$vMap[#key = current()]/#value"/>
</xsl:attribute>
</xsl:template>
</xsl:stylesheet>
when applied on the following XML document (as you didn't provide any):
<t foo="X">
<a foo="A">
<b foo="B"/>
</a>
<c foo="C"/>
</t>
produces the wanted, correct result:
<t foo="8">
<a foo="1">
<b foo="2"/>
</a>
<c foo="3"/>
</t>
Explanation: Appropriate use of the XSLT current() function.
II. XSLT 1.0 solution using keys for speed
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:key name="kValFromKey" match="entry/#value" use="../#key"/>
<xsl:variable name="vrtfMap">
<entry key="A" value="1"/>
<entry key="B" value="2"/>
<entry key="C" value="3"/>
<entry key="X" value="8"/>
</xsl:variable>
<xsl:variable name="vMap" select=
"document('')/*/xsl:variable[#name = 'vrtfMap']/*"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="#foo">
<xsl:variable name="vCur" select="."/>
<xsl:attribute name="foo">
<xsl:for-each select="document('')">
<xsl:value-of select="key('kValFromKey', $vCur)"/>
</xsl:for-each>
</xsl:attribute>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the same XML document (above), the same correct result is produced.
Explanation:
Use of <xsl:for-each select="document('')"> to set the current document to the stylesheet, so that the key() function will use the key index built for this document.
Saving the node matched by the template in a variable so that we can use it inside the xsl:for-each -- current() cannot be correctly used here, because it gets the current node on which xsl:for-each operates.
UPDATE: The OP has now clarified in a comment that his biggest problem is finding the maximum.
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:variable name="vrtfMap">
<entry key="A" value="1"/>
<entry key="B" value="2"/>
<entry key="C" value="3"/>
</xsl:variable>
<xsl:variable name="vMap" select=
"document('')/*/xsl:variable[#name = 'vrtfMap']/*"/>
<xsl:template match="/">
<xsl:variable name="vDoc" select="."/>
<xsl:variable name="vFoosMapped"
select="$vMap[#key = $vDoc/*/*/#foo]"/>
<max>
<xsl:value-of select=
"$vFoosMapped
[not($vFoosMapped/#value > #value)]
/#value
"/>
</max>
</xsl:template>
</xsl:stylesheet>
When given this XML document (the one provided by the OP lacks a singlr top element):
<t>
<tag foo="A">apples</tag>
<tag foo="C">oranges</tag>
<tag foo="B">trees</tag>
</t>
the wanted, correct result is produced:
<max>3</max>
Remark: A more efficient way of calculating maximum (or minimum -- in a similar way) in XSLT 1.0 is to do this:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:variable name="vrtfMap">
<entry key="A" value="1"/>
<entry key="B" value="2"/>
<entry key="C" value="3"/>
</xsl:variable>
<xsl:variable name="vMap" select=
"document('')/*/xsl:variable[#name = 'vrtfMap']/*"/>
<xsl:template match="/">
<xsl:variable name="vDoc" select="."/>
<xsl:variable name="vFoosMapped"
select="$vMap[#key = $vDoc/*/*/#foo]"/>
<max>
<xsl:for-each select="$vFoosMapped">
<xsl:sort select="#value" data-type="number" order="descending"/>
<xsl:if test="position() = 1">
<xsl:value-of select="#value"/>
</xsl:if>
</xsl:for-each>
</max>
</xsl:template>
</xsl:stylesheet>
Another question, why can't I indent my code? I'm putting spaces but
it's not working.
This is a SO bug that they failed to fix for many months.
Most probably you are using IE. If your version is 9, then do the following:
Press F12.
In the window that pops up click on the right-most menu and select: "Document mode: IE9 Standards"
Now you should be able to see the code with indentation.