Implementation Inheritance and Delegation in p6i

• A subclass may add inst. vars.
• A subclass may add/override methods.

  bbuf_peeki = class implements bbuf_peek extends bbuf_basei
    peek = method({full,mid}b:self{-}) replies(int) 
      reply(b.arr[b.opt])
    end peek
  end bbuf_basei
  

• A subclass may specify supplementary daemon methods for state maintainance (as in [Ishikawa]).

  bbuf_hli = class implements bbuf_hl extends bbuf_basei
    after get{mid}, put{mid} use hilow
    hilow = method({mid}b:self{high,low})
      if b.cnt>=b.size/2 then b!{high} else b!{low} end
    end hilow
  end bbuf_hli