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+module lqueen
+
+//	The Queens Problem, slow version.
+
+import StdEnv
+	
+BoardSize :== 8 // The size of the chessboard.
+
+//	Finding all solutions for the queens problem.
+	
+Queens::Int [Int] [[Int]] -> [[Int]]
+Queens row board boards
+	| row>BoardSize	= [board:boards]
+	| otherwise		= TryCols BoardSize row board boards
+
+//	The second alternative of TryCols is added to make sure Save is never
+//	called with an empty list.
+	
+TryCols::Int Int [Int] [[Int]] -> [[Int]]
+TryCols 0 row board boards	= 	boards
+TryCols col row [] boards	= 	TryCols (col-1) row [] queens
+where 
+	queens	= Queens (row+1) [col] boards
+		
+TryCols col row board boards
+	| Save col 1 board	= 	TryCols (col-1) row board queens					 
+	| otherwise			= 	TryCols (col-1) row board boards
+where 
+	queens	= Queens (row+1) [col : board] boards
+		
+
+Save::Int Int [Int] -> Bool
+Save c1 rdiff [c2]	=  cdiff<>0 && cdiff<>rdiff && cdiff<> 0 - rdiff
+where
+	cdiff = c1 - c2
+		
+Save c1 rdiff [c2:cols]	
+	| cdiff==rdiff || cdiff==0 || cdiff==0-rdiff	= 	False
+	| otherwise										= 	Save c1 (inc rdiff) cols
+where 
+	cdiff = c1 - c2
+		
+
+/*	The Start Rule: Calculate the list of solutions, show the first
+	solution and the length of that list.
+*/
+
+Start::(Int,[Int])
+Start = (length solutions, hd solutions)
+	where 
+		solutions = Queens 1 [] []
+