binary mekso operator: Let the inputs X1 and X2 be sets in the same universal set O; then the result of this operator applied to them is X1^c
\cup X, where for any A \subseteq O, Ac = O \setminus A.
binary mekso operator: Let the inputs X1 and X2 be sets in the same universal set O; then the result of this operator applied to them is X1^c
\cap X, where for any A \subseteq O, Ac = O \setminus A.
non-logical connective/mekso operator - of arity only 1 xor 2: set (absolute) complement, or set exclusion (relative complement). Unary: X2 ^C; binary: X1\setminusX.