Re: [R] Inf +1i vs 1+Inf*1i

From: Martin Maechler <maechler_at_stat.math.ethz.ch>
Date: Wed 13 Apr 2005 - 18:17:00 EST

>>>>> "Robin" == Robin Hankin <r.hankin@soc.soton.ac.uk> >>>>> on Wed, 13 Apr 2005 08:51:19 +0100 writes:

    Robin> Hi
    Robin> If I have

    Robin> a <- Inf + 1i

    Robin> then

    Robin> Re(a) is Inf, and Im(a) is 1, as expected.

    Robin> But if

    Robin> b <- 1 + Inf * 1i,

    Robin> then

    Robin> Im(b) = Inf , as expected, but Re(b) = NaN, which I didn't expect.

    Robin> Why this asymmetry?

I think this is a (very long standing) buglet in our complex arithmetic, since you can directly see

> 1+ 1i*Inf

  [1] NaN+Infi

    Robin> How to define an object with Re(b)=1, Im(b)=Inf?

{Oscar already mentioned b <- complex(real=1, im=Inf) }

Martin Maechler, ETH Zurich



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