"Brickman Brick" <ano### [at] anonymousorg> wrote in message 
news:4afab1ab@news.povray.org...
> Hello,
>
> I stumbled on some possible strange behaviour in the switch statement. I
> just want to verify if I am doing something wrong or POV-Ray.
>

Hi.
I use and abuse the switch statement quite a lot and I've not found any 
problems with it, so I suspect that you're doing something wrong, though you 
haven't provided enough info to really be sure of that.


> The switch statement is placed inside a loop to calculate a value of a
> variable many times.
>
> Here is a short example of the code I wrote. I omitted the necessary
> #break statements for readability.
>
> #switch (MySwitchValue)
> #case (1) //do something
> #case (2) //do something else
> #case (3) //etc1
> #case (0) //etc2
> #else
> #end
>
> Now this code works perfectly fine most of the time. Only sometimes it
> breaks and it seems that a #case (1) statement is just partly executed.
> After that, it continues just as expected.

My first suspect would be the calculated variable. Are you sure it 
definitely results in an integer value that will match one of the #case 
statements? If it's actually a decimal value then it may be slipping through 
to the #else statement. Beware that it's easy to fool yourself into thinking 
that you're getting an integer value by using #debug str(MySwitchValue,1,3) 
which will round the value to 3 decimals, which is not necessarily close 
enough to trip the #case statement.

Otherwise I think you'll need to find out the exact circumstances that 
causes it to break (using strategically placed debug statements), or at 
least provide a cut-down, but complete example that would enable someone 
else to replicate the problem. If it only fails 1 in 1000 times then provide 
an example with a loop that's large enough to consistently fail.


> Now when I do the following the code works again as expected.
>
> #switch (MySwitchValue)
> #debug "MyMessage"
> #case (1) //do something
> #case (2) //do something else
> #case (3) //etc1
> #case (0) //etc2
> #else
> #end
>
> Moving the #case (0) right in front of #case (1) also works.
> This case gives me the impression that the order seems important. On the
> other hand the example with the #debug statement indicates the opposite.
> Also, the docs say I may put the clauses in any order I want.
>

This sounds quite odd. When you have explored all other possible causes. it 
may be worth considering that the file or that your installation may be 
corrupt in some way. I have occasionally had wierd things happen where 
simply deleting and manually rekeying lines have cured the problem. I've 
rationalised this by believing that I may have accidentally typed an 
invisible hex character into the file that's corrupted it, or that it's 
somehow been corrupted by a disk read or write error. If you think the 
application may have gotten corrupted, then you may want to consider 
reinstalling it. I'd wait for a bit before exploring these more radical 
ideas though as someone else might come up with other ideas.

Regards,
Chris B.

Post a reply to this message