Bug 4621 – [FO] rounding for duration *|div number

Bug 4621 - [FO] rounding for duration *|div number

Summary:

[FO] rounding for duration *|div number

Status:	CLOSED FIXED

Product:	XPath / XQuery / XSLT
Component:	Functions and Operators 1.0
Version:	Recommendation
Platform:	PC Windows XP

Importance:	P2 normal
Target Milestone:	---
Assigned To:	Ashok Malhotra
QA Contact:	Mailing list for public feedback on specs from XSL and XML Query WGs

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Blocks:
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Reported:	2007-06-10 23:38 UTC by Michael Kay
Modified:	2007-11-16 09:18 UTC (History)
CC List:	0 users (show)

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Description Michael Kay 2007-06-10 23:38:54 UTC

This arises from bug 713 (member-only) against the XSLT test suite.

What is the correct result of xs:yearMonthDuration('-P1M')*0.5, or
xs:yearMonthDuration('-P1M') div 2? 

The spec says (10.6.3, 10.6.4) "The result is rounded to the nearest month. For
a value v, 0 <= v < 0.5 rounds to 0; 0.5 <= v < 1.0 rounds to 1." It's not
clear from that which way the rounding works for negative numbers.

My proposal would be to follow the rules of the round() function, so -0.5
rounds to 0. Specifically, the result should be the yearMonthDuration whose
length in months is equal to round() applied to result of multiplying/dividing
the length in months of $arg1 by the value of $arg2.

Comment 1 Ashok Malhotra 2007-06-11 13:33:06 UTC

Makes sense.  In fact, we should say that the result is computed using
fn:round().

Comment 2 Michael Kay 2007-06-12 20:31:39 UTC

Proposed change:

1. Change the summary of the two functions from

Summary: Returns the result of [multiplying|dividing] the value of $arg1 by
$arg2. The result is rounded to the nearest month. For a value v, 0 <= v < 0.5
rounds to 0; 0.5 <= v < 1.0 rounds to 1.

to

Summary: Returns the result of [multiplying|dividing] the value of $arg1 by
$arg2. The result is rounded to the nearest month.

2. Add immediately after the summary of each function, the paragraph:

The result is the xs:yearMonthDuration whose length in months is equal to the
result of applying the fn:round function to the value obtained by
[multiplying|dividing] the length in months of $arg1 by the value of $arg2.

Comment 3 Michael Kay 2007-06-27 14:58:16 UTC

This wording was accepted by the WGs on 27 June 2007

Comment 4 Michael Kay 2007-07-31 20:20:09 UTC

Erratum FO-E12 has been drafted.