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Date: Tue, 15 Jan 2008 11:06:42 +0000

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Date: Tue, 15 Jan 2008 11:06:42 +0000

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http://www.w3.org/Bugs/Public/show_bug.cgi?id=5251 ------- Comment #2 from mike@saxonica.com 2008-01-15 11:06 ------- After writing the proposal in comment #1 and sleeping on it, I realize that the approach of defining these functions in terms of simpler functions such as substring() and concat() could be taken further. Without relying on any definition of "match" or "minimal match", we can define the functions contains(), starts-with(), and ends-with() as follows: contains(): return the result of the XPath expression: some $M in 0 to string-length($arg1), $N in 0 to string-length($arg1) satisfies compare(substring($arg1, $M, $N), $arg2, $coll) eq 0 starts-with(): return the result of the XPath expression some $N in 0 to string-length($arg1) satisfies compare(substring($arg1, 1, $N), $arg2, $coll) eq 0 ends-with(): return the result of the XPath expression some $N in 0 to string-length($arg1) satisfies compare(substring($arg1, $N), $arg2, $coll) eq 0 substring-before(): return the result of the XQuery expression: if ((contains($arg1, $arg2, $coll)) then let $Z := string-length($arg1) let $M := min((1 to $Z)[some $L in 0 to $Z satisfies compare(substring($arg1, ., $L), $arg2, $coll) eq 0]) (: M is the position of the start of the first match :) let $L := max((1 to $Z)[compare(substring($arg1, $M, .), $arg2, $coll) eq 0]) (: L is the length of the longest match at this position :) let $I := max((0 to $L)[compare(substring($arg1, $M + $I, $L - $I), $arg2, $coll) eq 0] (: I is the number of ignorable characters at the start of this match, so M+I is the position of the start of the minimal match :) return substring($arg1, 1, $M + $I - 1). (: return the substring containing all characters before the start of the minimal match :) else "" substring-after(): : return the result of the XQuery expression: if ((contains($arg1, $arg2, $coll)) then let $Z := string-length($arg1) let $M := min((1 to $Z)[some $L in 0 to $Z satisfies compare(substring($arg1, ., $L), $arg2, $coll) eq 0]) (: M is the position of the start of the first match :) let $L := max((1 to $Z)[compare(substring($arg1, $M, .), $arg2, $coll) eq 0]) (: L is the length of the longest match at this position :) let $I := max((0 to $L)[compare(substring($arg1, $M, $L - $I), $arg2, $coll) eq 0] (: I is the number of ignorable characters at the endof this match, so M+L-I is the position of the end of the minimal match :) return substring($arg1, $M + $L - $I) (: return all characters after the end of the first minimal match :) else ""Received on Tuesday, 15 January 2008 11:06:49 GMT

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