On Thu, 14 Mar 2019 at 04:41, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Dean Rasheed <dean.a.rasheed@gmail.com> writes:
> > I'm amazed that jacana's asinh() returned -0 for an input of +0.
>
> Even more amusingly, it returns NaN for acosh('infinity'), cf
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=jacana&dt=2019-03-14%2003%3A00%3A34
>
> Presumably that means they calculated "infinity - infinity" at some
> point, but why?
>
Given the -0 result, I don't find that particularly surprising. I
suspect lots of formulae would end up doing that without proper
special-case handling upfront.
It looks like that's the only platform that isn't POSIX compliant
though, so maybe it's not worth worrying about.
Regards,
Dean