How to check if given comma separated values is ascending numerical sequence - xslt-2.0

Question

I would like to check if given comma separated value is ascending numeric sequence.
Input XML:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<isSequence>
<seq name="a" value="1, 2, 3"/>
<seq name="b" value="3, 1, 5, 6"/>
<seq name="c" value="15, 16, 18, 0"/>
<seq name="d" value="21, 22, 23, 24, 25"/>
<seq name="e" value="A, B, C"/>
</isSequence>
</root>
I have tried below code
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="xs"
version="2.0">
<xsl:template match="/">
<xsl:for-each select="root/isSequence/seq">
<xsl:if test="subsequence(#value, 0)">
<xsl:value-of select="#name"/> is an ascending numeric sequence
</xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
Expected Result
a is an ascending numeric sequence
d is an ascending numeric sequence

Answer 1

Assuming you are looking for an integer sequence then I think (in XSLT 3) this can be expressed as
<xsl:template match="seq[let $items := tokenize(#value, ',\s+')!xs:integer(.) return every $p in 1 to count($items) satisfies $items[$p] = $items[1] + ($p - 1)]">
<xsl:value-of select="#name"/><xsl:text> is an ascending numeric sequence
</xsl:text>
</xsl:template>
Full example (https://xsltfiddle.liberty-development.net/6r5Gh2H)
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="#all"
expand-text="yes"
version="3.0">
<xsl:mode on-no-match="shallow-skip"/>
<xsl:strip-space elements="*"/>
<xsl:output method="text"/>
<xsl:template match="seq[let $items := tokenize(#value, ',\s+')!xs:integer(.) return every $p in 1 to count($items) satisfies $items[$p] = $items[1] + ($p - 1)]">
<xsl:value-of select="#name"/><xsl:text> is an ascending numeric sequence
</xsl:text>
</xsl:template>
</xsl:stylesheet>
In XSLT 2 with XPath 2 I don't think you have let to express that compactly in a match pattern but you can of course use a variable at XSLT level:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="#all"
version="2.0">
<xsl:strip-space elements="*"/>
<xsl:output method="text"/>
<xsl:template match="seq[every $i in tokenize(#value, ',\s+') satisfies $i castable as xs:integer]">
<xsl:variable name="items" select="for $item in tokenize(#value, ',\s+') return xs:integer($item)"/>
<xsl:if test="every $p in 1 to count($items) satisfies $items[$p] = $items[1] + ($p - 1)">
<xsl:value-of select="#name"/><xsl:text> is an ascending numeric sequence
</xsl:text>
</xsl:if>
</xsl:template>
</xsl:stylesheet>
http://xsltransform.hikmatu.com/bFDb2BU