Linda, ^._1 NB.The log of a negative number is complex 0j3.14159
>________________________________ > Fra: Linda Alvord <[email protected]> >Til: [email protected] >Sendt: 11:22 torsdag den 17. januar 2013 >Emne: Re: [Jprogramming] Hermitian from triangular > >Isn't the log of negative numbers indefined? > >This is a problem: > > %1&o.+0 >_ > %1&o.-0 >_ > >This is nice! > > %1&o.%_ >_ > %1&o.%__ >__ > > >The csc is very small for negative numbers close to zero and very large for >very small positive numbers. > >Linda > >-----Original Message----- >From: [email protected] >[mailto:[email protected]] On Behalf Of Bo Jacoby >Sennt: Thursday, January 17, 2013 3:37 AM >To: [email protected] >Subject: Re: [Jprogramming] Hermitian from triangular > >Henry, How is negative zero different from positive zero when taking the >log? > ^.%__ NB. log -0 >__ > ^.%_ NB. log +0 >__ > > >- Bo > > >>________________________________ >> Fra: Henry Rich <[email protected]> >>Til: [email protected] >>Sendt: 0:38 torsdag den 17. januar 2013 >>Emne: Re: [Jprogramming] Hermitian from triangular >> >>Negative zero makes sense as a last vestige of gradual underflow; and >anyway, it's well-behaved: it looks like 0 except when you take the log, >reciprocal, or square root. In any normal computation, it goes away. In >contrast, NaN messes up anything it touches. >> >>I think we've had negative 0 in J forever. If NaN is a data virus, -0 is a >virus that has been inserted into our DNA. >> >>Henry Rich >> >>On 1/16/2013 4:45 PM, Raul Miller wrote: >>> On Wed, Jan 16, 2013 at 4:35 PM, Henry Rich <[email protected]> wrote: >>>> Negative zero isn't a bug, it's a feature that numerical types, >>>> especially William Kahan, wanted to get into IEEE-754 to help out >>>> some things. I'm not expert enough to explain. >>> >>> Something similar could be said about NaN. >>> >>---------------------------------------------------------------------- >>For information about J forums see http://www.jsoftware.com/forums.htm >> >> >> >---------------------------------------------------------------------- >For information about J forums see http://www.jsoftware.com/forums.htm > >---------------------------------------------------------------------- >For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
