(declare bool type)
(declare tt bool)
(declare ff bool)

(program bool_or ((a bool) (b bool)) bool
         (match a
                (tt tt)
                (ff b)))

(declare is_or (! a bool (! b bool (! sc (^ (bool_or a b) tt) type))))
(declare is_or_2 (! a bool (! b bool (! sc (provided (bool_or a b) tt) type))))