Thanks for the history lesson. :-) This does bring up another difference between an initialized value of NaN and undefined:
NaN != NaN, while undefined == undefined > On Aug 3, 2017, at 1:00 AM, Dave Fisher <dave2w...@comcast.net> wrote: > > I hate this Macbook’s touch top bar which puts a send button directly above > the delete key. > >> On Aug 2, 2017, at 2:50 PM, Dave Fisher <dave2w...@comcast.net> wrote: >> >> Hi Folks, >> >> A peanut gallery look at NaN which is really a bit encoding for various >> kinds of floating point number errors like underflow, overflow, divided by >> 0, etc. In my Fortran past life we used XMISS as a special valu > > Value. Essentially undefined. > > IEEE had very particular definitions and Apple published a book about SANE. > > At any rate what you guys are observing is by design: NaN always results in > false in any comparison. And it is a number. But it is not a number in > floating point so much as it is an error condition. > > https://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-comparisons-returning-false-for-ieee754-nan-values > > https://people.eecs.berkeley.edu/~wkahan/ieee754status/IEEE754.PDF > > My father complained about when the IBM 360 came out in the early 1960’s he > had to go to doubles because the IBM architecture went from 6 - 6 bit words > for a single to 4 - 8 bit words. The practical result was twice as much > magnetic tape both length and number of reals. > > Regards, > Dave > >> >>> On Aug 1, 2017, at 3:21 PM, Greg Dove <greg.d...@gmail.com> wrote: >>> >>> Yes it does. NaN is an 'instance' of the Number type (even though it is >>> 'Not a Number' ;) ) >>> >>> >>> On Wed, Aug 2, 2017 at 10:18 AM, Harbs <harbs.li...@gmail.com> wrote: >>> >>>> Interesting. >>>> >>>> I’m not sure that I realized that NaN passes that test. Does it? >>>> >>>>> On Aug 2, 2017, at 1:12 AM, Greg Dove <greg.d...@gmail.com> wrote: >>>>> >>>>> I agree undefined works the same as NaN for many things for example, but >>>> it >>>>> fails on very basic things like if (x is Number) >>>> >>>> >> >
