note description: "Unbounded stacks implemented as linked lists" legal: "See notice at end of class." status: "See notice at end of class." names: linked_stack, dispenser, linked_list; representation: linked; access: fixed, lifo, membership; contents: generic; date: "$Date$" revision: "$Revision$" class LINKED_STACK [G] inherit STACK [G] undefine replace, copy, is_equal select remove, put, item end LINKED_LIST [G] rename item as ll_item, remove as ll_remove, put as ll_put export {NONE} all {LINKED_STACK} cursor, start, forth, go_to, index, first_element, last_element, valid_cursor {ANY} count, readable, writable, extendible, make, wipe_out, off, after undefine readable, writable, fill, append, linear_representation, prune_all, is_inserted redefine extend, force, duplicate end create make feature -- Access item: G -- Item at the first position do check not_empty: not is_empty end Result := first_element.item end feature -- Element change force (v: like item) -- Push `v' onto top. do put_front (v) end extend (v: like item) -- Push `v' onto top. do put_front (v) end put (v: like item) do put_front (v) end feature -- Removal remove -- Remove item on top. do start ll_remove end feature -- Conversion linear_representation: ARRAYED_LIST [G] -- Representation as a linear structure -- (order is reverse of original order of insertion) local old_cursor: CURSOR do old_cursor := cursor from create Result.make (count) start until after loop Result.extend (ll_item) forth end go_to (old_cursor) end feature -- Duplication duplicate (n: INTEGER): like Current -- New stack containing the `n' latest items inserted -- in current stack. -- If `n' is greater than `count', identical to current stack. require else positive_argument: n > 0 local counter: INTEGER old_cursor: CURSOR list: LINKED_LIST [G] do if not is_empty then old_cursor := cursor from create Result.make list := Result start until after or counter = n loop list.finish list.put_right (ll_item) counter := counter + 1 forth end go_to (old_cursor) end end note library: "EiffelBase: Library of reusable components for Eiffel." copyright: "Copyright (c) 1984-2006, Eiffel Software and others" license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)" source: "[ Eiffel Software 356 Storke Road, Goleta, CA 93117 USA Telephone 805-685-1006, Fax 805-685-6869 Website http://www.eiffel.com Customer support http://support.eiffel.com ]" end -- class LINKED_STACK