/tutorial/backtracking/logigram/constraint_group.e

  1-- See the Copyright notice at the end of this file.
  2--
  3class CONSTRAINT_GROUP
  4	--
  5	-- manages a group of constraints
  6	-- group of constraints shares the same variables
  7	--
  8
  9creation {ANY}
 10	make
 11
 12feature {ANY}
 13	var_set: HASHED_SET[ITEM_VAR]
 14			-- the variables of the group
 15
 16	logic: LINKED_LIST[CONSTRAINT_LOGICAL]
 17			-- the logic constraints (equal, not equal, greater, lesser)
 18
 19	couple: LINKED_LIST[CONSTRAINT_COUPLE]
 20			-- the couple constraints (yes, no)
 21
 22	make is
 23			-- creation
 24		do
 25			create var_set.make
 26			create logic.make
 27			create couple.make
 28		end
 29
 30	add (constraint: CONSTRAINT; set: HASHED_SET[ITEM_VAR]) is
 31			-- record the constraint and the set of variables
 32		local
 33			clog: CONSTRAINT_LOGICAL; cpl: CONSTRAINT_COUPLE
 34		do
 35			var_set.union(set)
 36			clog ?= constraint
 37			if clog /= Void then
 38				logic.add_last(clog)
 39			else
 40				cpl ?= constraint
 41				check
 42					cpl /= Void
 43				end
 44				couple.add_last(cpl)
 45			end
 46		end
 47
 48	union (other: like Current) is
 49			-- add the data of other to current
 50		do
 51			var_set.union(other.var_set)
 52			logic.append_collection(other.logic)
 53			couple.append_collection(other.couple)
 54		end
 55
 56	build_nodes (builder: MASK_BUILDER): BACKTRACKING_NODE is
 57			-- deduce backtracking graph from the current constraints
 58		do
 59			Result := get_node(builder, var_set.lower)
 60		end
 61
 62feature {}
 63	get_node (builder: MASK_BUILDER; ivar: INTEGER): BACKTRACKING_NODE is
 64			-- deduce backtracking graph from the current constraints
 65			-- ivar is the number of the var that will be evaluated
 66		do
 67			if ivar > var_set.upper then
 68				-- not a variable then check if configuration is allowed
 69				Result := get_node_if_true(builder)
 70			else
 71				-- loop on variable value
 72				Result := get_node_of_var(builder, ivar)
 73			end
 74		end
 75
 76	get_node_of_var (builder: MASK_BUILDER; ivar: INTEGER): BACKTRACKING_NODE_OR_LIST is
 77			-- generate the alternative values of the variable ivar
 78		local
 79			v: ITEM_VAR; n: BACKTRACKING_NODE
 80		do
 81			v := var_set.item(ivar)
 82			from
 83				v.start
 84			until
 85				v.is_off
 86			loop
 87				n := get_node(builder, ivar + 1)
 88				if n /= Void then
 89					Result := create {BACKTRACKING_NODE_OR_LIST}.make(n, Result)
 90				end
 91				v.next
 92			end
 93		end
 94
 95	get_node_if_true (builder: MASK_BUILDER): BACKTRACKING_NODE is
 96		local
 97			i: INTEGER
 98		do
 99			-- check if logic constraints are ok
100			from
101				i := logic.lower
102			until
103				i > logic.upper or else not logic.item(i).to_boolean
104			loop
105				i := i + 1
106			end
107			if i > logic.upper then
108				-- logics constraints are ok 
109				-- then build the mask corresponding to the couple constraints
110				builder.clear
111				from
112					i := couple.lower
113				until
114					i > couple.upper or else not builder.is_ok
115				loop
116					couple.item(i).build_masks(builder)
117					i := i + 1
118				end
119				if builder.is_ok then
120					-- possible solution
121					Result := builder.get_node
122				end
123			end
124		end
125
126end -- class CONSTRAINT_GROUP
127--
128-- ------------------------------------------------------------------------------------------------------------------------------
129-- Copyright notice below. Please read.
130--
131-- This file is free software, which comes along with SmartEiffel. This software is distributed in the hope that it will be
132-- useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
133-- You can modify it as you want, provided this footer is kept unaltered, and a notification of the changes is added.
134-- You are allowed to redistribute it and sell it, alone or as a part of another product.
135--
136-- Copyright(C) 1994-2002: INRIA - LORIA (INRIA Lorraine) - ESIAL U.H.P.       - University of Nancy 1 - FRANCE
137-- Copyright(C) 2003-2005: INRIA - LORIA (INRIA Lorraine) - I.U.T. Charlemagne - University of Nancy 2 - FRANCE
138--
139-- Authors: Dominique COLNET, Philippe RIBET, Cyril ADRIAN, Vincent CROIZIER, Frederic MERIZEN
140--
141-- http://SmartEiffel.loria.fr - SmartEiffel@loria.fr
142-- ------------------------------------------------------------------------------------------------------------------------------