Jeff,

Computer Science geekspeak.

In English,

De Morgan's law says that

Select all units that are not both German and Infantry

is exactly the same as saying

Select all units that are not German or not Infantry.

It is a general purpose logical equivalence that can be used anywhere logic statements are used (e.g. IF statements in any programming language, Matching Property strings in VASSAL). It allows you to swap between using AND and OR and moves the NOT from applying to the whole statement to applying to each component. Very useful in a limited application like VASSAL which doesn't have a complete _expression_ evaluator (i.e. no parentheses and no NOT operator).

Cheers,
Brent.


*********** REPLY SEPARATOR ***********

On 22/04/2006 at 5:19 PM Jeffrey A. Wise wrote:
Huh? <:/
  ----- Original Message -----
  From: Brent Easton
  To: [email protected]
  Sent: Saturday, April 22, 2006 5:04 PM
  Subject: Re: [vassalengine] Question on properties


  Yes, of course you are right.,

  I'ts been a long, long, long time since college, but this is one of the most useful things I ever learnt there!

  Cheersm
  Brent.

  *********** REPLY SEPARATOR ***********

  On 22/04/2006 at 11:44 PM Joel Uckelman wrote:
  Thus spake "Brent Easton":
  >
  > >2- does a negation operator exist
  > >for example: !(property1=a && property2=b)
  >
  > Don't forget Boole's law:
  >
  >   !(property1=a && property2=b)
  >
  > is equivalent to
  >
  >   property1!=a || property2!=b
  >

  Not really on topic, but as a logician I can't help but comment:
  The logical equivalence here is called De Morgan's Law, not
  Boole's Law. :)

  --
  J.



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