Any Octave users? What is this code snippet actually doing?

[Bruce Labitt]

On 04/06/2013 04:58 PM, Michael ODonnell wrote:
>
>> kmax=1;
>> kfactor=(kmax-1.0)/delta/(orderbc+1.0)/delbc^orderbc;
>> Unless matlab treats floats and ints differently than most other
>> languages, I'd say its a bug because zero over anything is always zero.
>
> Shame on anybody who'd intentionally code something like
> that without also providing a comment about such a seemingly
> counterintuitive approach.  >-/ Let's hope it's simply a bug...
>
> Out of morbid curiosity, how does Octave report the value of
> kfactor after
>
>     kmax=1
>     kfactor=(kmax-1.0)
>
>    ??
>   
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>
kfactor = 0 is reported by octave in debug mode.

That's a long bit of code

kfactor=(kmax-1.0)/delta/(orderbc+1.0)/delbc^orderbc;

just to set it to zero.  Clearly a bug, or just plain wrong and not 
thought through.  Drives me nuts, since this construct was used for the 
x, y, and z axes.

Guess I'll have to contact one of the authors of the book.  The graduate 
student that wrote the code has since graduated.  (Got her PhD int 
2010.)  Humph, you'd think the code samples for something this 
complicated would be better.

\rant on
The level of commenting in the code sample is not up to teaching 
standards, IMHO.  If you are doing something tricky, write a descriptive 
comment on it!  (I can't even remember tricky stuff I did last week 
without good comments.)  Please, everyone, don't write ultra dense code 
like this, spaces are your friend!

dx(:,2:je_tot,2:ke_tot)=C1ex(:,2:je_tot,2:ke_tot).* 
dx(:,2:je_tot,2:ke_tot)+ 
C2ex(:,2:je_tot,2:ke_tot).*((hz(:,2:je_tot,2:ke_tot)-hz(:,1:je_tot-1,2:ke_tot))-
(hy(:,2:je_tot,2:ke_tot)-hy(:,2:je_tot,1:ke_tot-1)))./delta;

Especially if there are 5 more lines just like it, with slightly 
differing indices, with no spaces in between!
\rant off

As you were.  :)