Re: [gobo-eiffel-develop] Adding tree support to gobo

[Eric B. <er...@go...>]

Einar Karttunen wrote:
>=20
> I think of inheriting from DS_CONTAINER=2E DS_TRAVERSABLE presents
> problems as trees can be traversed in many orders=2E I plan to include
> pre-, post-, inorder and Lindst=F6m-traversing=2E

You could arbitrarily choose one of them to implement
the routines from DS_TRAVERSABLE and provide other
external cursors for the other kind of traversals=2E
For example:

  new_cursor: DS_TREE_CURSOR [G] is
        -- New external cursor for traversal
        -- (Use preorder traversal by default=2E)
     do
        Result :=3D new_preorder_cursor
     end

  new_preorder_cursor: DS_PREORDER_TREE_CURSOR [G] is
        -- New external cursor for preorder traversal
    do
        !! Result=2Emake (Current)
    ensure
        =2E=2E=2E
    end

  new_postorder_cursor: DS_POSTORDER_TREE_CURSOR [G] is
        -- New external cursor for postorder traversal
    do
        !! Result=2Emake (Current)
    ensure
        =2E=2E=2E
    end

  =2E=2E=2E

--=20
Eric Bezault
mailto:ericb@gobosoft=2Ecom
http://www=2Egobosoft=2Ecom