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 From: Daniel J Sebald Subject: Re: About diagonal matrices Date: Sun, 01 Mar 2009 16:05:05 -0600 User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20041020

```Jaroslav Hajek wrote:
```
```On Sun, Feb 22, 2009 at 12:49 AM, Daniel J Sebald
```
```
```
```Here's a bug:

octave:18> complex(0,Inf) - Inf
ans = -Inf + Infi
octave:23> complex(0,-Inf) + Inf
ans = Inf - Infi

That should be -Inf + NaNi, I'd think.
```
```

Why?
```
```
Eh, that looks right.  I must have gotten lost in looking at all the Inf
scenarios.

```
```

```
```Same sort of thing here:

octave:28> complex(0,-Inf) / 0
warning: division by zero
ans = NaN - NaNi

should be NaN - Infi.

```
```

Not really. The reason is that the zero is converted to complex zero
prior to the division, i.e. there is no actual complex/real operation
implemented in Octave. An implementation using the direct algorithm
would, of course, be superior.
```
```
OK, complex(3,4)/complex(0,0) = NaN + NaNi.  I guess it is better as is.  In
some sense, there shouldn't be a NaN + NaNi, just NaN, otherwise there is all
kind of implied meaning.  Same with Inf + Infi.  (Just exactly along what path
does the limit follow?)

Alright, so:

octave:24> complex(3,0) / 0
warning: division by zero
ans = NaN - NaNi
octave:25> 3 / 0
warning: division by zero
ans = Inf

Anyone recall John Travolta when he started out in Welcome Back Kotter?  "I'm so
confuuuuused".

Dan

```