On Sat, Oct 14, 2017 at 11:00 PM, Dirk Ziegemeyer <dirk at ziegemeyer.de> wrote: > Is it possible at all to define a typeclass key_value_store with the method search_value and then to declare map as an instance of this typeclass? No, "map" is a constructor, not a type, so you would need a constructor class not a typeclass. Mark