The term {tt (lognot $tau$)} denotes the bit-wise logical not of the object denoted by $tau$.
(<- (Logandc1 ?X ?Y) (Logand (Lognot ?X) ?Y)) (<- (Logandc2 ?X ?Y) (Logand ?X (Lognot ?Y))) (<- (Lognand ?X ?Y) (Lognot (Logand ?X ?Y))) (<- (Lognor ?X ?Y) (Lognot (Logior ?X ?Y))) (<- (Logorc1 ?X ?Y) (Logior (Lognot ?X) ?Y)) (<- (Logorc2 ?X ?Y) (Logior ?X (Lognot ?Y)))