:: deftheorem Def11 defines and3b TWOSCOMP:def 11 :
for b₁ being Function of (3 -tuples_on BOOLEAN),BOOLEAN holds
( b₁ = and3b iff for x, y, z being Element of BOOLEAN holds b₁ . <*x,y,z*> = (('not' x) '&' ('not' y)) '&' z );