Author mark.dickinson
Recipients Rhamphoryncus, christian.heimes, gmcastil, gvanrossum, mark.dickinson, tim.peters
Date 2008-01-20.22:54:34
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Message-id <1200869676.13.0.848344794912.issue1640@psf.upfronthosting.co.za>
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No:  IEEE-754r and the C99 standard both say clearly that atanh(1) should be infinity 
and atanh(-1) should be -infinity, and furthermore that the 'divide-by-zero' exception 
should be raised rather than the 'invalid' exception.  It's a singularity, just like 
log(0).  (This makes even more sense viewed from the perspective of complex 
arithmetic, where atanh is defined at all points in the complex plane except -1 and 1, 
where it has log-type singularities.)

The general idea is that it's meaningful to set atanh(1) = infinity because that's 
what the limit of atanh(x) is as x approaches 1 from below;  similarly for atanh(-1) 
and log(0).
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Date User Action Args
2008-01-20 22:54:36mark.dickinsonsetspambayes_score: 0.00421649 -> 0.00421649
recipients: + mark.dickinson, gvanrossum, tim.peters, Rhamphoryncus, christian.heimes, gmcastil
2008-01-20 22:54:36mark.dickinsonsetspambayes_score: 0.00421649 -> 0.00421649
messageid: <1200869676.13.0.848344794912.issue1640@psf.upfronthosting.co.za>
2008-01-20 22:54:34mark.dickinsonlinkissue1640 messages
2008-01-20 22:54:34mark.dickinsoncreate