lists.hs

    choice AddVoter : ContractId Doodle
      with
        voter: Party
      controller organizer
        do
          assertMsg "this doodle has been opened for voting, cannot add voters" (not open)
          create this with voters = voter::voters

    choice RemoveVoter : ContractId Doodle
      with
        voter: Party
      controller organizer
        do
          assertMsg "this doodle has been opened for voting, cannot remove voters" (not open)
          create this with voters = DA.List.delete voter voters


    preconsuming choice IssueInvites : ContractId Doodle
      controller organizer 
        do
          assertMsg "this doodle has been opened for voting, cannot issue any more invites" (not open)
          DA.Traversable.mapA (\voter -> create DoodleInvite with doodleName = this.name, organizer = this.organizer, voter = voter) voters
          -- archive self
          create this with open = True