If I weren't on vacation I would volunteer a solution using
divide-and-conquer recursion: see if the first half of the two strings is
the same, then split into quarters, etc.
Following that line below pure XSLT 1.0 stylesheet gives
the common prefix of two strings.
Mismatch position is just its string-length+1.
(Just in case of email-gateway modifications:
http://www.stamm-wilbrandt.de/en/xsl-list/CommonPrefix.xsl)
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
<xsl:output method="xml"/>
<xsl:template name="CommonPrefix">
<xsl:param name="a"/>
<xsl:param name="b"/>
<xsl:variable name="A" select="string-length($a)"/>.
<xsl:variable name="B" select="string-length($b)"/>.
<xsl:choose>
<xsl:when test="$A < $b">
<xsl:call-template name="CommonPrefixRec">
<xsl:with-param name="a" select="$a"/>
<xsl:with-param name="b" select="substring($b,1,$A)"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:call-template name="CommonPrefixRec">
<xsl:with-param name="a" select="substring($a,1,$B)"/>
<xsl:with-param name="b" select="$b"/>
</xsl:call-template>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template name="CommonPrefixRec">
<xsl:param name="a"/>
<xsl:param name="b"/>
<xsl:variable name="mid" select="floor(string-length($a) div 2)"/>
<xsl:variable name="a1" select="substring($a,1,$mid)"/>)
<xsl:variable name="b1" select="substring($b,1,$mid)"/>)
<xsl:choose>
<xsl:when test="not(substring($a,1,1) = substring($b,1,1))"/>
<xsl:when test="$a1 = $b1">
<xsl:value-of select="$a1"/>
<xsl:call-template name="CommonPrefixRec">
<xsl:with-param name="a" select="substring($a,$mid + 1)"/>
<xsl:with-param name="b" select="substring($b,$mid + 1)"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:call-template name="CommonPrefixRec">
<xsl:with-param name="a" select="substring($a,1,$mid)"/>
<xsl:with-param name="b" select="substring($b,1,$mid)"/>
</xsl:call-template>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template match="/">
<out>
<xsl:call-template name="CommonPrefix">
<xsl:with-param name="a" select="'abcdefghijklmnopqrstuvwxyz'"/>
<xsl:with-param name="b" select="'abcdefghijklmnopqrstuvwxy0'"/>
</xsl:call-template>
</out>
</xsl:template>
</xsl:stylesheet>
Mit besten Gruessen / Best wishes,
Hermann Stamm-Wilbrandt
Developer, XML Compiler
WebSphere DataPower SOA Appliances
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"Michael Kay"
<mike(_at_)saxonica(_dot_)co
m> To
<xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com>
09/11/2009 06:17 cc
PM
Subject
RE: [xsl] Finding first difference
Please respond to between 2 text strings
xsl-list(_at_)lists(_dot_)mu
lberrytech.com
If I weren't on vacation I would volunteer a solution using
divide-and-conquer recursion: see if the first half of the two strings is
the same, then split into quarters, etc.
Regards,
Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay
-----Original Message-----
From: James A. Robinson [mailto:jim(_dot_)robinson(_at_)stanford(_dot_)edu]
Sent: 11 September 2009 04:53
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: Re: [xsl] Finding first difference between 2 text strings
On Thu, 10 Sep 2009 20:41:21 -0700 I wrote:
<
< Wow, that's... very very impressive. So you're replacing
regular < expression values with placeholders in both
strings, then wrapping ever < character in $bb with a regex
expression, e.g., '(a)?', to finally < perform a regex
replacement on $aa? What does the leading colon < do?
One last comment. I timed 100 iterations comparing two 520
character strings, and both functions run in effectively the
same time, but your solution doesn't run into the stack
overflow problem that mine does at the 520+ character range.
Jim
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
James A. Robinson
jim(_dot_)robinson(_at_)stanford(_dot_)edu
Stanford University HighWire Press http://highwire.stanford.edu/
+1 650 7237294 (Work) +1 650 7259335 (Fax)
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