:: deftheorem Def12 defines nand3 TWOSCOMP:def 12 :
for b₁ being Function of (3 -tuples_on BOOLEAN),BOOLEAN holds
( b₁ = nand3 iff for x, y, z being Element of BOOLEAN holds b₁ . <*x,y,z*> = 'not' ((x '&' y) '&' z) );