> but it seems clear to me that _. represents 'an unknown number', > not 'a non-number'. As such, we can see some of the rules it > obeys in 602:
It is jarring to me to see "rules" and _. or NaN used together. To wit: * x=x is 0 * u>v is 0 but v<u is 1 when u=infinity and v=NaN * after assigning y to x it is possible for x to be not equal to y These are things I observed in C compilers, different things on different compilers. ----- Original Message ----- From: Henry Rich <[EMAIL PROTECTED]> Date: Thursday, February 7, 2008 9:18 Subject: RE: [Jbeta] Another incompatibility: _ >. _. WAS: _ <. _. To: 'Beta forum' <[email protected]> > I think we need to get off this idea of thinking of _. as > 'not a number'. That's IEEE talk, not J. IEEE > supports a > whole family of NaNs, but that's immaterial to J. > > In J, the definition is enigmatic: > > The indeterminate _. results from expressions such > as _-_ > (infinity minus infinity) and from expressions (such as 3+_.) > in which an indeterminate argument occurs. > > but it seems clear to me that _. represents 'an unknown number', > not 'a non-number'. As such, we can see some of the rules it > obeys in 602: > > _. ^ 0 > 1 > > (correct in my opinion) > > 0 * _. > 0 > > (again correct in my opinion) > > 0 ^ _. > 0 > > (incorrect in my opinion, since 0 ^ 0 is 1 and 0 ^ _1 is _) > > _ >: _. > 0 > > (incorrect IMO - this is what we have been talking about) > > Henry Rich > > PS. > > _. ^ _. > |limit error > > I wonder what's happening there? > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of Kip Murray > > Sent: Thursday, February 07, 2008 11:21 AM > > To: Beta forum > > Subject: RE: [Jbeta] Another incompatibility: _ >. _. WAS: _ > <. _. > > > > I think _. as an answer signals the question didn't make > > sense. As _. > > is _not a number_ (it could be Lucciano Pavarotti's high C), > > operations > > like x + _. and x >. _. are undefined. Another user > could be > > depending > > on _. as a signal the operation was undefined. > > > > Of course, depending on _. for anything can be questioned, > > and you can > > ask why _ , which also is not a number, gets special > treatment. The > > difference is, we know what rules _ obeys. See for > example > > The Extended > > Real Number System, Section 1.23 of Walter Rudin's Principles > of > > Mathematical Analysis, Third Edition. > > > > Kip Murray > > > > On Thu, 7 Feb 2008, Henry Rich wrote: > > > > (Note that the subject of the original message contained > > a typo <. for >., though the text was correct.) > > > > I don't see the logic. x+_. > > is _. because if you don't know what _. is, you don't > > know the result, even if x is _ . But > with _ >. _. > > you know the result, no matter what _. is: _ >. x > > is _ for all x. So _ would be a reasonable answer. > > > > You said earlier that _. <: _ should > produce 1, > > which seems to conform to my argument above. If > > _. is recognized as less-or-equal _, I think it > > needs to follow that _. >. _ is > _ . > > > > The case that got me into this _. mess was > > > > 1 2 3 _ I. _. > > > > where I had a list that I thought I had terminated > with a > > high value, but I found that _. is higher > yet. It > > would simplify analysis and description if _. were > > consistently recognized as not being bigger than > _ . > > > > Henry Rich > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] > > > [mailto:[EMAIL PROTECTED] On Behalf Of > Roger Hui > > > Sent: Wednesday, February 06, 2008 10:45 PM > > > To: Beta forum > > > Subject: Re: [Jbeta] Another incompatibility: _ > <. _. > > > > > > The answer should be _. for the same reason that > x+_. > > should be _. . > > > That is, for all numeric atoms x, _. should be > the answer for > > > > > > x + _. > > > x >. _. > > > x <. _. > > > _. + x > > > _. >. x > > > _. <. x > > > > > > > > > > > > ----- Original Message ----- > > > From: Henry Rich <[EMAIL PROTECTED]> > > > Date: Wednesday, February 6, 2008 6:55 > > > Subject: [Jbeta] Another incompatibility: _ > <. _. > > > To: 'Beta forum' <[email protected]> > > > > > > > I also just got bit by > > > > > > > > _ >. _. > > > > _. > > > > > > > > This gave _ in 601. And in 602, > > > > > > > > _. >. _ > > > > _ > > > > > > > > > > > > I think both results should be _ ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
