[hhandoko]

The Scala example, yes... The Elixir one? Is it actually a Monad? I figure it's simply destructuring + pattern matching (against the value of the first tuple value, :ok or :error atom).

To expand a bit more, it's not like Scala's `Either[T, U]` where we're limited to a pair of types, I think you can return other atom values (but use :ok and :error) as a convention.

Also, there is an Elixir library I'm using that's a closer in spirit to Scala's for-comprehension called `monadex`. Example below:

    result = success(comment_params)
             ~>> fn p  -> link_reply_to_id(p)  end
             ~>> fn p  -> create_changeset(p)  end
             ~>> fn cs -> assert_changeset(cs) end
             ~>> fn cs -> insert_changeset(cs) end