# Re: Novice question about flair and geometry debugging

From: Santana, Mario <msantana_at_slac.stanford.edu>
Date: Sun, 28 Oct 2012 14:50:46 -0700

Hi Ray,

On Oct 28, 2012, at 2:35 PM, Ray F. Cowan wrote:

> Hi Mario,
>
> Thanks so much for the pointer to the problem! Now I have a better
> understanding of what I was requesting on my region cards.
>
> For the target, I wanted the union of the two bodies, tgtcyl and tgtcone.
>
>> TARGET 5 +tgtcyl +tgtcone
>
> which I now interpret as meaing the intersection of tgtcyl and tgtcone, not
> their union. To get the union of these two bodies I write
>
>> TARGET 5 +tgtcyl | +tgtcone

This is correct '|' is the union operator in FLUKA input syntax

> which I interpret as "points in tgtcone OR in tgtcyl".
> However, regarding the void region, I want the void body minus both the
> tgtcyl and tgtcone bodies. My original specification
>
>> VOID 5 +void -tgtcyl -tgtcone
>
> still seems to me to be correct. I interpret this as
> "void and not tgtcyl and not tgtcone".

Yes, now this is right. The VOID region is inside void body (thus +void) minus
(==>negation) the target definition.
If you negate a union 'A OR B', per boolean logics results to NOT(A OR B) = NOT(A) AND NOT(B)
thus resulting into the definition that you write above.

> This is, I think,
> equivalent to your second suggestion for void below, which I
> repeat here:
>
>> VOID 5 | +void -(+tgtcyl +tgtcone)
>
> Let me know if you disagree. Many, many thanks for pointing
> out my (now obvious!) mistake.

I disagree with the latest statement. If you use parentheses, then inside the parentheses you just have to write the logics
of the TARGET region (a union of bodies, in your case).

>
> Thank you,
> --Ray

Mario
Received on Mon Oct 29 2012 - 23:10:43 CET

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