-- Three Drinking Logicians, see http://spikedmath.com/445.html

VARS 1,2,3

LAW  Top

OBS  a: 1
     b: 2
     c: 3

TRUE?
  {}
  a knows that ~(1 & 2 & 3)

VALID?
  [ ! ~ a knows whether (1 & 2 & 3) ]
  (a,b,c) comknow that 1

VALID?
  [ ! ~ a knows whether (1 & 2 & 3) ]
  [ ! ~ b knows whether (1 & 2 & 3) ]
  c knows whether (1 & 2 & 3)

VALID?
  ( < ! ~ a knows whether (1 & 2 & 3) >
    < ! ~ b knows whether (1 & 2 & 3) >
    < ! c knows that (1 & 2 & 3) > Top )
  iff
    (1 & 2 & 3)