Subject: Re: [xsl] XPath: comparison of 0.0e0 and +0.0e0 From: Stefan Krause <stf@xxxxxxxx> Date: Mon, 20 Jun 2011 00:37:25 +0200 
> I think its strange that the spec requires ambiguous results of atan2 for zerovalued arguments: > > The expression math:atan2(+0.0e0, 0.0e0) returns 0.0e0. > The expression math:atan2(+0.0e0, 0.0e0) returns math:pi(). > > The expression math:atan2(0.0e0, 0.0e0) returns 0.0e0. > The expression math:atan2(0.0e0, 0.0e0) returns math:pi(). This is a bug in the spec, see http://www.w3.org/Bugs/Public/show_bug.cgi?id=11549 Stefan Am 20.06.2011 um 00:17 schrieb Imsieke, Gerrit, letex: > > > On 20110619 23:08, Stefan Krause wrote: >>> [b&] Out of interest, >>> why do you need to distinguish them? >> >> Because atan2(y,x) treats them different, see [1]. I try to implement this behavior in XSLT 2.0. > > I think its strange that the spec requires ambiguous results of atan2 for zerovalued arguments: > > The expression math:atan2(+0.0e0, 0.0e0) returns 0.0e0. > The expression math:atan2(+0.0e0, 0.0e0) returns math:pi(). > > The expression math:atan2(0.0e0, 0.0e0) returns 0.0e0. > The expression math:atan2(0.0e0, 0.0e0) returns math:pi(). > > Then atan2 is no longer a function, mathematically. > > If, in an attempt to disambiguate the function, the B1O results were not required, you could simply return > x*y for x=B10, y=B10. > > If the spec is flawed and should actually read: > > The expression math:atan2(+0.0e0, +0.0e0) returns 0.0e0. > The expression math:atan2(+0.0e0, 0.0e0) returns 0.0e0. > The expression math:atan2(0.0e0, +0.0e0) returns math:pi(). > The expression math:atan2(0.0e0, 0.0e0) returns math:pi(). > > then I donbt see another way than reverting to some tricks such as cast each argument to xs:string and look up the corresponding result. > > Gerrit
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