On Sun, Mar 2, 2008 at 7:45 AM, Roger Hui <[EMAIL PROTECTED]> wrote: > T=: 27*^.2 > > (spoiler alert.) > > > What is interesting about T=:27*^.2 ? In IEEE 64-bit > floating point calculation, for all y>:T, 1=tanh y > (and _1=tanh -y) and T is the smallest number with > this property. > > tanh=: (^ - [EMAIL PROTECTED]) % (^ + [EMAIL PROTECTED])
I would rather defined tanh as tanh1 =: 7&o. If you use this definition, then the above statement is not true. In fact, (tanh1 0.2 + T) is still not exactly one. This is similary to what I get if I use the tanh function in the GNU libc, which is supposed to be very precise, so I assume that for such large values, tanh1 gives a more precise result than your tanh function (the difference is minute of course). Ambrus ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
