:: deftheorem Def10 defines and3a TWOSCOMP:def 10 :
for b₁ being Function of (3 -tuples_on BOOLEAN),BOOLEAN holds
( b₁ = and3a iff for x, y, z being Element of BOOLEAN holds b₁ . <*x,y,z*> = (('not' x) '&' y) '&' z );