+record powerset_carrier (A: objs1 SET) : Type1 ≝ { mem_operator: A ⇒_1 CPROP }.
+interpretation "powerset low" 'powerset A = (powerset_carrier A).
+notation "hvbox(a break ∈. b)" non associative with precedence 45 for @{ 'mem_low $a $b }.
+interpretation "memlow" 'mem_low a S = (mem_operator ? S a).