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Date: Sat, 13 Jun 2015 19:37:01 +0000

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Message-ID: <bug-28795-523-ADzXcVOUiQ@http.www.w3.org/Bugs/Public/>

Date: Sat, 13 Jun 2015 19:37:01 +0000

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Message-ID: <bug-28795-523-ADzXcVOUiQ@http.www.w3.org/Bugs/Public/>

https://www.w3.org/Bugs/Public/show_bug.cgi?id=28795 --- Comment #2 from Michael Kay <mike@saxonica.com> --- Here's a suggested definition of the same-key relation: The same-key relation is defined as follows. Two atomic values A and B are the same key if the expression (A eq B) is true, with the following exceptions and caveats: * If evaluation of the expression (A eq B) fails with a dynamic error or type error, then A and B are not the same key. * If A and B are both instances of one of the types xs:string, xs:untypedAtomic, or xs:anyURI, then they are the same key if codepoint-compare(A, B) eq 0. * If A and B are both instances of one of the types xs:dateTime, xs:date, xs:time, xs:gYear, xs:gYearMonth, xs:gMonth, xs:bMonthDay, or xs:gDay, then: ** if they are instances of different primitive types, then they are not the same key ** if one of the values has a timezone and the other does not, then they are not the same key ** if both have a timezone, they are the same key if and only if (A eq B) ** if neither has a timezone, they are the same key if and only if (A eq B) NOTE: although the rules for comparison in this case make reference to the implicit timezone in the dynamic context, the result is the same regardless of the implicit timezone. * If A and B are both instances of one of the types xs:float, xs:double, or xs:decimal (which includes xs:integer), then [subject to bug 28795]: ** If A is the xs:double or xs:float value NaN, and B is the xs:double or xs:float value NaN, then A and B are equal. ** Positive infinity equals positive infinity, and negative infinity equals negative infinity. ** Except for NaN and positive or negative infinity, the two values A and B are equal if and only if they represent the same mathematical quantity. Effectively both A and B are converted to instances of xs:decimal using an implementation of xs:decimal whose value space provides sufficient precision and scale to contain the value space of xs:double (and therefore xs:float) precisely; the values are then compared within this value space. ** It follows that positive and negative zero are equal. NOTE: These rules are chosen (and differ from the rules for the comparison operator “eq”) to achieve three aims: ** Comparing two atomic values never raises an error ** Equality is commutative and transitive ** Equality comparison is context-free (the result does not depend on anything in the static or dynamic context) -- You are receiving this mail because: You are the QA Contact for the bug.Received on Saturday, 13 June 2015 19:37:04 UTC

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