[Spiral] add fibonacci spiral

Spiral.hs

@@ -1,4 +1,4 @@
-module XMonadContrib.Spiral (spiral) where
+module XMonadContrib.Spiral (spiral, fibSpiral) where
 
 import Graphics.X11.Xlib
 import Operations
@@ -16,7 +16,7 @@ import XMonad
 --                       spiral (1000 % 1618) ]
 --
 spiral :: Rational -> Layout
-spiral rat = Layout { doLayout = \sc ws -> return $ zip ws (divideRects rat (length ws) East $ sc),
+spiral rat = Layout { doLayout = \sc ws -> return $ zip ws (divideRects (repeat rat) (length ws) East $ sc),
                       modifyLayout = \m -> fmap resize (fromMessage m)}
 
     where resize Expand = let newRat = ((numerator rat + 10) % (denominator rat))
@@ -26,6 +26,24 @@ spiral rat = Layout { doLayout = \sc ws -> return $ zip ws (divideRects rat (len
                               normRat = if numerator newRat < 0 then rat else newRat in
                           spiral normRat
 
+fibs :: [Integer]
+fibs = 1 : 1 : (zipWith (+) fibs (tail fibs))
+
+fibRatios :: [Rational]
+fibRatios = ratios fibs
+    where
+      ratios (x:y:rs) = (x % y) : ratios (y:rs)
+      ratios _ = []
+
+fibSpiral :: Rational -> Layout
+fibSpiral scale = Layout { doLayout = fibLayout,
+                           modifyLayout = \m -> fmap resize (fromMessage m) }
+    where
+      fibLayout sc ws = return $ zip ws (divideRects (map (* scale) . reverse . take len $ fibRatios) len East sc)
+          where len = length ws
+      resize Expand = fibSpiral $ (11 % 10) * scale
+      resize Shrink = fibSpiral $ (10 % 11) * scale
+
 data Direction = East | South | West | North
 
 nextDir :: Direction -> Direction
@@ -34,10 +52,11 @@ nextDir South = West
 nextDir West = North
 nextDir North = East
 
-divideRects :: Rational -> Int -> Direction -> Rectangle -> [Rectangle]
+divideRects :: [Rational] -> Int -> Direction -> Rectangle -> [Rectangle]
-divideRects r n dir rect | n <= 1 = [rect]
+divideRects [] _ _ _ = []
+divideRects (r:rs) n dir rect | n <= 1 = [rect]
                               | otherwise = case divideRect r dir rect of
-                                     (r1, r2) -> r1 : (divideRects r (n - 1) (nextDir dir) r2)
+                                     (r1, r2) -> r1 : (divideRects rs (n - 1) (nextDir dir) r2)
 
 divideRect :: Rational -> Direction -> Rectangle -> (Rectangle, Rectangle)
 divideRect ratio East (Rectangle x y w h) = let (w1, w2) = chop ratio (fromIntegral w) in