Kenneth wrote:
> "Kenneth" <kdw### [at] earthlinknet> wrote:
> 
>> Something like,
>> "For example, if you use a series of #case or #range clauses with no #
breaks
>> in-between, the first clause that evaluates TRUE will force all subseq
uent
>> clauses to evaluate TRUE as well (regardless of their intrinsic TRUE/F
ALSE
>> conditional state), in a sort of cascade--until a #break/#else/#end is

>> encountered." Or something similar.
>>
> 
> And this 'cascade effect' can also affect the behavior of #else, kind o
f a
> 'gotcha' (as I discovered, now that I halfway-know what I'm doing!)  I'
ll use
> the "N=prime" code as an example (with a few additions of my own)...
> 
> #declare N = 6;
> #switch(N)
>        #case(2)
>          // if 2, do this
>          #debug "I like this number a lot!\n"
>        #case(3)
>        #case(5)
>        #case(7)
>          // if 2, 3, 5, or 7, do this
>          #debug "N is prime\n"
>        #break
>        #range(0,10)
>          #debug "N is non-prime\n"
>        #range(20,30)
>          #debug "range(20,30) is also TRUE\n"
>        #range(40,50)
>          #debug "range(40,50) is also TRUE\n"
>        // #break
>        #else // do this for anything over 10
>          #debug "Oops, I don't know the primes >10 by heart\n"
>      #end
> 
> Note that I purposely commented-out the final #break clause. (I say thi
s because
> initially, I didn't think it was necessary. But it is.)
> 
> The docs about #else say, "It is only executed if the clause before it 
was a
> false clause."
> 
> Let's say N=6. The first clause to be evaluated TRUE is #range(1,10).
 Now
> without thinking, it might appear that the final #range(40,50) would be

> evaluated false (because N doesn't fall in its range). But because of t
he
> 'cascading TRUES' of the #ranges above it, it's actually TRUE. And, con
tinuing,
> the #else conditional in this case is also forced TRUE (if that's the c
orrect
> term), and #else's token is also printed to messages. So the #break cla
use
> before #else is a necessity, to get an expected outcome from it.
> 
	The doc explicitly states the opposite: "parsing continues until a
#break, *#else* or #end directive is reached", so this is a bug
(either in povray or in the docs).

		Jerome
-- 
mailto:jeb### [at] freefr
http://jeberger.free.fr
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