note
	description: "Two-way lists, kept sorted."
	library: "Free implementation of ELKS library"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	names: sorted_two_way_list, sorted_struct, sequence
	representation: linked
	access: index, cursor, membership, min, max
	contents: generic
	date: "$Date: 2018-11-14 15:15:17 +0000 (Wed, 14 Nov 2018) $"
	revision: "$Revision: 102463 $"

class 
	SORTED_TWO_WAY_LIST [G -> COMPARABLE]

inherit
	TWO_WAY_LIST [G]
		undefine
			has,
			search,
			is_inserted
		redefine
			prune_all,
			extend,
			new_chain
		end

	SORTED_LIST [G]
		undefine
			move,
			remove,
			before,
			go_i_th,
			isfirst,
			start,
			finish,
			readable,
			islast,
			first,
			prune,
			after,
			last,
			off,
			prune_all,
			copy,
			new_cursor
		end

create 
	make,
	make_from_iterable


create {SORTED_TWO_WAY_LIST}
	make_sublist

feature -- Element change

	extend (v: like item)
			-- Put v at proper position in list.
			-- Move cursor to newly inserted item.
		do
			search_after (v)
			put_left (v)
			back
		end
	
feature -- Removal

	prune_all (v: like item)
			-- Remove all items identical to v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- Leave cursor off.
		do
			from
				start
				search (v)
			until
				off or else v < item
			loop
				remove
			end
			if not off then
				finish
				forth
			end
		end
	
feature -- Transformation

	sort
			-- Sort all items.
			-- Has O(count * log (count)) complexity.
		local
			no_change: BOOLEAN
			gap: INTEGER_32
			left_cell, cell: like first_element
			left_cell_item, cell_item: like item
		do
			if not is_empty then
				from
					gap := count * 10 // 13
				until
					gap = 0
				loop
					from
						no_change := False
						go_i_th (1 + gap)
					until
						no_change
					loop
						no_change := True
						from
							left_cell := first_element
							cell := active
						until
							cell = Void
						loop
							if left_cell /= Void then
								left_cell_item := left_cell.item
								cell_item := cell.item
								if cell_item < left_cell_item then
									no_change := False;
									cell.put (left_cell_item);
									left_cell.put (cell_item)
								end
								left_cell := left_cell.right
							end
							cell := cell.right
						end
					end
					gap := gap * 10 // 13
				end
			end
		end
	
feature -- Status report

	sorted: BOOLEAN
			-- Is the structure sorted?
		local
			c: CURSOR
			prev: like item
		do
			Result := True
			if count > 1 then
				from
					c := cursor
					start
					check
							not off
					end
					prev := item
					forth
				until
					after or not Result
				loop
					Result := prev <= item
					prev := item
					forth
				end
				go_to (c)
			end
		end
	
feature {SORTED_TWO_WAY_LIST}{TWO_WAY_LIST}{LINKED_LIST}{DYNAMIC_CHAIN} -- Implementation

	new_chain: like Current
		obsolete "Use explicit creation instead. See also explanations for `duplicate`. [2018-11-30]"
			-- A newly created instance of the same type.
			-- This feature may be redefined in descendants so as to
			-- produce an adequately allocated and initialized object.
		do
			create Result.make
		end
	
note
	copyright: "Copyright (c) 1984-2018, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., 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 SORTED_TWO_WAY_LIST

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