布尔环
We use the operations ¬, N"p", (negation), ∧, K"pq", (conjunction or meet), ∨, A"pq", (disjunction or join), →, C"pq", (implication), ↔, E"pq", (biconditional), +, J"pq" (exclusive disjunction or Boolean ring addition), ↛, L"pq", (nonimplication), ?: (the ternary ) and the constant unary functions 0 and 1. Moreover, we need the threshold functions