Used simplifier rules: min-one: ⊦ (∅ ++ a).min = a;%max-one: ⊦ (∅ ++ a).max = a;% ⊦ (s ++ a) -- a = s -- a; (s)% ⊦ ∅ -- a = ∅; (s)% ⊦ #(∅ ++ a) = 1; (s)