AmigActive 3/AACD03.BIN/AACD/Programming/sofa/archive/exml.lha/exml/examples/ebook/gobo_ext/ds_linked_tree_cursor.e

Text File | 1999-04-13 | 7KB | 325 lines

indexing
    description:"Cursor class for flexible iteration through%
                    %DS_LINKED_TREE objects"
    status:        "See notice at end of class."
    author:        "Andreas Leitner"

class
    DS_LINKED_TREE_CURSOR [G]

inherit
    DS_CURSOR [G]

creation
    make

feature -- Initialization
feature {NONE} -- Initialization

    make (tree: like container) is
            -- Create a new cursor for `tree'.
        require
            list_not_void: tree /= void
        do
            container := tree
            before_root := True
        ensure
            container_set: container = tree;
            before_root: before_root
        end;

feature -- Access

    container: DS_LINKED_TREE [G]

feature -- Status report

    is_root: BOOLEAN is
            -- Is cursor on root item?
        require
            not_off: not off
        do
            Result := (not off) and then (container.root_cell = current_cell)
        end

    depth: INTEGER is
        require
            not_off: not off
        do
            Result := current_cell.depth
        end


    is_leaf: BOOLEAN is
        require
            not_off: not off
        do
            Result := current_cell.is_leaf
        end

    is_valid: BOOLEAN is
            -- Is cursor valid?
            -- (A cursor might become invalid if `container'
            -- has been modified during traversal.)
            -- (from DS_CURSOR)
        local
            a_cell: like current_cell
        do
            -- TODO: !!!
            --check False end
            Result := True
        end

    before_root: BOOLEAN
    after_leaf: BOOLEAN

feature -- Cursor movement

    to_root is
            -- Move cursor to a leaf(reachable from the current cell).
        do
            before_root := False
            current_cell := container.root_cell
            after_leaf := current_cell = Void
            update_children_cursor
        end;

    down is
        require
            no_leaf: not is_leaf
            current_child_not_off: not child_off
        do
            if
                before_root
            then
                current_cell := container.root_cell
            else
                current_cell := children_cursor.current_cell
            end
            after_leaf := current_cell = Void
            update_children_cursor
        end

    up is
        local
            p: like current_cell
        do
            p := current_cell
            if after_leaf then
                -- TODO: !!!
                check False end
            else
                current_cell := current_cell.parent
            end
            update_children_cursor
            children_cursor.go_to_cell (p)

        end


    off: BOOLEAN is
            -- Is there no item at cursor position?
        do
            Result := current_cell = Void
        end

    item: G is
            -- Item at cursor position
        do
            Result := current_cell.item
        end;

    has (v: like item): BOOLEAN is
            -- Has the subtree item v?
            -- (comparsion by reference)
        local
            cs: like Current
        do
            if
                v = item
            then
                Result := True
            else
                if
                    not is_leaf
                then
                    from
                        cs := clone (Current)
                        cs.update_children_cursor
                        cs.child_start
                    until
                        cs.child_off or Result = True
                    loop
                        cs.down
                        if
                            cs.has (v) = True
                        then
                            Result := True
                        end
                        cs.up
                        cs.child_forth
                    end
                end
            end
        end


feature {DS_LINKED_TREE_CURSOR, DS_LINKED_TREE} -- Implementation
    current_cell: DS_LINKED_TREE_CELL [G]

    children_cursor: DS_LINKED_TREE_CHILDREN_CURSOR [G]
            -- cursor to children.
            -- if you store a reference to this `children_cursor'
            -- be aware that it does not automatically update
            -- when you traverse up or down in the tree

    children: DS_LINKED_TREE_CHILDREN_LIST [G] is
        do
            Result := current_cell.children
        end


feature -- {NONE}
    update_children_cursor is
        do
            if
                off
            then
                children_cursor := Void
            else
                children_cursor := current_cell.children.new_cursor
            end
        end

feature -- Children Cursor
    child_index: INTEGER is
            -- Index of current position
        do
            Result := children_cursor.index
        end

    child_item: G is
            -- Item at cursor position
        do
            Result := children_cursor.item
        end

feature -- Status report

    child_after: BOOLEAN is
            -- Is there invalid position to right of cursor?
        do
            Result := children_cursor.after
        end

    child_before: BOOLEAN is
            -- Is there no valid position to left of cursor?
        do
            Result := children_cursor.before
        end

    is_first_child: BOOLEAN is
            -- Is cursor on the first item?
        do
            Result := children_cursor.is_first
        end

    is_last_child: BOOLEAN is
            -- Is cursor on the last child_item?
        do
            Result := children_cursor.is_last
        end

    is_valid_child: BOOLEAN is
            -- Is cursor valid?
        do
            Result := children_cursor.is_valid
        end

    child_off: BOOLEAN is
            -- Is there no child_item at cursor position?
        do
            Result := children_cursor.off
        end

    valid_child_index (i: INTEGER): BOOLEAN is
            -- Is `i' a valid index value?
        do
            Result := children_cursor.valid_index (i)
        end

feature -- Cursor movement

    child_back is
            -- Move cursor to previous position.
        do
            children_cursor.back
        end

    child_finish is
            -- Move cursor to last position.
        do
            children_cursor.finish
        end

    child_forth is
            -- Move cursor to next position.
        do
            children_cursor.forth
        end

    child_go_to (i: INTEGER) is
            -- Move cursor to `i'-th position.
        do
            children_cursor.go_to (i)
        end

    child_search_back (v: G) is
            -- Move to first position at or before current
            -- position where `child_item' and `v' are equal.
            -- (Use `searcher''s comparison criterion from `children_cursor.container'.)
            -- Move `before' if not found.
        do
            children_cursor.search_back (v)
        end

    child_search_forth (v: G) is
            -- Move to first position at or after current
            -- position where `child_item' and `v' are equal.
            -- (Use `searcher''s comparison criterion from `children_cursor.container'.)
            -- Move `after' if not found.
        do
            children_cursor.search_forth (v)
        end

    child_start is
            -- Move cursor to first position.
        do
            children_cursor.start
        end

feature -- Element change

    child_put (v: G) is
            -- Replace child_item at cursor position by `v'.
        do
            children_cursor.put (v)
        end
feature

end -- class DS_LINKED_TREE_CURSOR

--|-------------------------------------------------------------------------
--| eXML, Eiffel XML Parser Toolkit
--| Copyright (C) 1999  Andreas Leitner
--| See the file forum.txt included in this package for licensing info.
--|
--| Comments, Questions, Additions to this library? please contact:
--|
--| Andreas Leitner
--| Arndtgasse 1/3/5
--| 8010 Graz
--| Austria
--| email: [e-mail]
--| web: http://exml.dhs.org
--|-------------------------------------------------------------------------