From bug-octave-request at bevo dot che dot wisc dot edu  Wed Sep  6 14:16:41 2000
Subject: real(Inf+Inf*i) vs imag(Inf+Inf*i) asymmetry
From: Rolf Fabian <fabian at tu-cottbus dot de>
To: "'bug-octave UWISC'" <bug-octave at bevo dot che dot wisc dot edu>
Date: Wed, 6 Sep 2000 14:17:23 -0500 (CDT)

Hi,

For my
:>version |- 2.1.14 (OS/2)
installation, I observe the following 'asymmetry' between
imag(x) and real(x) for no-finite input x.

I'm afraid that the problem also occurs with current V2.1.31

------ IMAG -------
:1>imag(Inf*i)		|-	Inf	OK
:2>imag(Inf+Inf*i)	|-	Inf	OK
:3>imag(Inf)		|-	 0	OK

------ REAL -------
:1>real(Inf)		|-	Inf	OK
:2>real(Inf+Inf*i)	|-	NaN	<<
:3>real(Inf*i)		|-	NaN	<<

In my eyes, the above 'imag' returns are correct,
whereas the '<<' are erraneous.

The problem seems NOT to come from 'real'. The underlying
reason seems to be, that the following assignment
is automatically converted

:>x=Inf+Inf*i	|- ans  x=NaN+Inf*i    <<

to a NaN real part,
with the consequence that

:>isnan(real(x))	|- ans=1
:>isnan(imag(x))	|- ans=0

results,
which leads to the imag/real asymmetry demonstrated above.

Rolf



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