Use XPath:Replace on first instance of a single character [duplicate] - xpath

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Match first only instance of a character [duplicate]
(1 answer)
Closed 3 years ago.
I'm trying to replace only the first instance of a character in a string like fred-3-1-2 with XPath::replace and replace it with a / so that the resulting string is fred/3-1-2. I cannot guarantee anything else about the original string other than that it will have one or more dashes in it. I'm having a ton of difficulty finding a regex pattern that works with XPath::replace and consistently matches only that particular first instance of -.
I feel like I came close with:
(?:.+?)(-)(?:.+)
But this also matches the full string as well, so it is no good.
Please do not offer solutions using anything but plain regular expressions that would work on https://regex101.com. The "flavor" of regex should abide by XPath/XQuery semantics (https://www.w3.org/TR/xmlschema-2/#regexs).

Answer 1

You can use:
replace('fred-3-1-2', '^([^-]*)-','$1/')
Check it. Result:
fred/3-1-2
Meaning:
From the start, match any non - character followed by one -
character, replace the match by the first captured group plus /
character
Do note: XPath/XQuery follows Perl regexp. The description in XML Schema you cite is extended in XPath/Xquery with the followings: "Matching the Start and End of the String", "Reluctant Quantifiers", "Captured Sub-Expressions", "Back-References"

Answer 2

Pure XPath 1.0 solution -- no regular expressions:
concat(substring-before('fred-3-1-2', '-'), '/', substring-after('fred-3-1-2', '-'))
In case the string is contained in a variable $s and it isn't known that it contains a -, then use:
concat(
substring(concat(substring-before($s, '-'), '/', substring-after($s, '-')),
1 div contains($s, '-')
),
substring($s, 1 div not(contains($s, '-')))
)
XSLT-based verification:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:variable name="s" select="'fred-3-1-2'"/>
<xsl:variable name="t" select="'fred+3+1+2'"/>
<xsl:template match="/">
<xsl:value-of select="concat(substring-before('fred-3-1-2', '-'), '/', substring-after('fred-3-1-2', '-'))"/>
=================
<xsl:value-of select=
"concat(
substring(concat(substring-before($s, '-'), '/', substring-after($s, '-')),
1 div contains($s, '-')
),
substring($s, 1 div not(contains($s, '-')))
)"/>
===============
<xsl:value-of select=
"concat(
substring(concat(substring-before($t, '-'), '/', substring-after($t, '-')),
1 div contains($t, '-')
),
substring($t, 1 div not(contains($t, '-')))
)"/>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on any XML file (not used), it evaluates the XPath expressions provided on this answer and produces the wanted, correct results: if the string contains - then its first (only) occurence in the string is replaced in the result of the evaluation; if the string doesn't contain any hyphens, then the result is the same string unchanged:
fred/3-1-2
=================
fred/3-1-2
===============
fred+3+1+2