Variables in Assura rule file

I want to ask a question about Assura DRC rules writing. Can variables
be defined and assigned to certain value more than once in the same
sequence without problems?

Here's an example:

A=geomAnd(B1 B2)
B=geomAndNot(C1 A1)
;
A=geomAnd(B1 B3)
C=geomOverlap(C2 C3)
;
if (! avSwitch( "Sw1" ) then
keepLayer(B)
)

if( !avSwitch( "Sw2" ) then
keepLayer(C)
)
;

How can A layer be defined twice at the same place!! Which one will be
stored? I can't understand it. It may be error in the rule file. As I
can basically understand, i think that variable A was overwritten and
no longer existing!! Isn't it?

Another question about keepLayer() , I read about it in Assura Command
Reference and unfortunately I couldn't understand that it has an
advantage! And can I consider the VLW as a window to display DRC
errors in it?

I'm originally Calibre user, and am a new user to Assura, so my
questions may look to be very basic, but it will help me a lot if I
got answers on them..

Thanks and best regards,
Ahmad.

 

Assura rule decks, like Diva rule decks, are SKILL scripts. The "rules"
are actually SKILL procedures that define tasks to be executed later.

The A in your example is a SKILL variable referring to a layer object,
not the layer itself. When you use A you are actually using the most
recent layer object which was assigned to A. While the compiler will
store the variable name "A" in the layer object, the name is not used to
find the layer object. The variable refers to the layer object directly,
not by name.

 

Thank you for your reply, but unfortunately, I couldn't understand
what do you mean!

In my example above, A has been overwritten (or defined again) without
any processing on it!! Is that valid? Or it may be a mistake?

Thanks in advance,
Ahmad,

 

Yes, it is valid.

It also doesn't make too much sense, as you are pointing out, and it could be a mistake.

Maybe A1 on line 2 was meant to be A ? Hard to tell anyway, without having the whole deck to look at.


Stéphane