Add ngon rooms

src/Geometry.hs

@@ -462,9 +462,9 @@ chainPairs xs = zip xs $ tail xs
 
 -- | Given a list of points, returns pairs of points linking the points into a
 -- loop.
-loopPairs :: [Point2] -> [(Point2,Point2)]
-loopPairs [] = error "tried to make loop with empty list of points"
-loopPairs [_] = error "tried to make loop with singleton list of points"
+loopPairs :: [a] -> [(a,a)]
+loopPairs [] = error "tried to make loop with empty list of elements"
+loopPairs [_] = error "tried to make loop with singleton list of elements"
 loopPairs (x:xs) = zip (x:xs) (xs ++ [x])
 -- | Test whether a point is in a cone.
 -- Note the pair is ordered.