> On Behalf Of John Randall ... > Henry Rich wrote: ... > > > If that's not off base, then the choice of the negative > > real axis for the branch cut is just an arbitrary programming > > decision. Wherever you put the branch cut, you should expect > > to have trouble that you will have to program around. Hoping that > > hardware support for -0 will bail you out of that trouble seems > > like wishful thinking to me: prone to disaster if you step > > over the line, and kludgy even if you get it to work somehow. > > You're right. It's probably better to think of local inverses. > However, most people don't want to use, say, the inverse of f(x)=x^2 > on the interval [_2,_1], they just want %: . Hardware support > ultimately does not replace thinking. > > > > > I'm thinking this is what Pepe meant when he said > > "This is like deja vu all over again." > > > And he's right. > > > > If people are really finding -0 to be the solution to real > > problems, I'd like to understand better how they arrange their > > processing to be sure they get good results. > > > > I hope I have given some kind of rationale: -/+0 are important for > expressing one-sided limits, a frequent consideration in some > important problems. If you are not involved with these problems, it > may seem unnecessary, slipshod, etc. I do not think there is anything > wrong with the way J handles it (by ignoring it). For the specialized > community which does a lot of floating-point calculations, it matters > more. >
One the one hand, I agree with John, and I had agreed with him before, that (at least the current machine combination of) hardware & software does not replace human mathematical thinking, and definitely not the IEEE 754 support for -/+ 0. One other hand, I am lazy by nature and prone to making silly mistakes; so, I prefer the hardware & software to do most of the math for me whenever reasonably possible. The -/+0 and limits subject have been discussed in the forums several times before. Henry, you surely must remember some of them; I definitely appreciated your contributions (I was educated by them). John has exhibited several advantages of adopting the IEEE support which I find quite convincing (search the forum: all IEEE; author randall). Yet it has not happen, although (the IEEE) -0 might sneak into J it is virtually useless. I can presume some potential reasons for not adopting it: 0. Backwards compatibility. However, J does not have a strong, to put it mildly, tradition in this regard. 1. It might be not that easy to implement. 2. It is not a priority. 3. It would make J less portable across different platforms. 4. There could be unavoidable consequential disadvantages linked to the adoption. Given what I know so far, I would go the IEEE way; and I, for one, would like to know counterarguments related to 4 (even if only for academic reasons). ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
