DeMorgan's Law(futval.cpp)

• Humans generally have a hard time comprehending logical conditions with not operators applied to and/or expressions.

  if (!(country == "USA"
        && state != "AK"
        && state != "HI"))
     shipping_charge = 20.00;
  

• DeMorgan's Law can be used to simplify these Boolean expressions.
• DeMorgan's Law has two forms:

  !(A && B)	is the same as	!A || !B
  !(A || B)	is the same as	!A && !B

• Pay particular attention to the fact that the and and or operators are reversed by moving the not inwards.
• Example:

  state != "AK" && state != "HI"
  

  means

  !(state == "AK") && !(state == "HI")
  

  Applying DeMorgan's Law to the original expression yields

  !(state == "AK" || state == "HI")