I assume it is if (unknownNumOrNaN != unknownNumOrNaN ) I have used things like if (unknownNumOrNaN *0 !=0) in the past but the above seems better
On Thu, Aug 3, 2017 at 6:20 PM, Harbs <harbs.li...@gmail.com> wrote: > I’m curious. How does that work? > unknownNumOrNaN != NaN will always be true > > > On Aug 3, 2017, at 1:37 AM, Josh Tynjala <joshtynj...@gmail.com> wrote: > > > > Good one! To avoid the overhead of the isNaN() function call, I > frequently > > rely on the fact that NaN != NaN. > > > > - Josh > > > > On Wed, Aug 2, 2017 at 3:32 PM, Harbs <harbs.li...@gmail.com> wrote: > > > >> 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) > >>>>>> > >>>>>> > >>>> > >>> > >> > >> > >
