Re: [Haskell-beginners] why is there no typeclass common to all containers?

There are several packages that define typeclasses for containers and, in particular, "map-like" things: * keys (no construction, no insertion) * Data.Containers from the mono-traversable package * EdisonAPI * https://github.com/commercialhaskell/jump (still in the works) Another somewhat related package is focus, which defines a common abstraction for various operations on a key-value pair in a map.