:: deftheorem Def13 defines nand3a TWOSCOMP:def 13 :
for b₁ being Function of (3 -tuples_on BOOLEAN),BOOLEAN holds
( b₁ = nand3a iff for x, y, z being Element of BOOLEAN holds b₁ . <*x,y,z*> = 'not' ((('not' x) '&' y) '&' z) );