:: deftheorem Def3 defines nand2a TWOSCOMP:def 3 :
for b₁ being Function of (2 -tuples_on BOOLEAN),BOOLEAN holds
( b₁ = nand2a iff for x, y being Element of BOOLEAN holds b₁ . <*x,y*> = 'not' (('not' x) '&' y) );