proc logic a b . .
   if a = 1 and b = 1
      r1 = 1
   .
   if a = 1 or b = 1
      r2 = 1
   .
   if a = 0
      r3 = 1
   .
   print r1 & " " & r2 & " " & r3
.
logic 0 0
logic 0 1
logic 1 0
logic 1 1
