September Morn Update

Task/Topological-sort/Haskell/topological-sort-1.hs

@@ -1,39 +1,44 @@
-import Data.List
-import Data.Maybe
-import Control.Arrow
-import System.Random
-import Control.Monad
+import Data.List ((\\), elemIndex, intersect, nub)
+import Control.Arrow ((***), first)
 
 combs 0 _ = [[]]
 combs _ [] = []
-combs k (x:xs) = map (x:) (combs (k-1) xs) ++ combs k xs
+combs k (x:xs) = ((x :) <$> combs (k - 1) xs) ++ combs k xs
 
 depLibs :: [(String, String)]
-depLibs = [("des_system_lib","std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee"),
-          ("dw01","ieee dw01 dware gtech"),
-          ("dw02","ieee dw02 dware"),
-          ("dw03","std synopsys dware dw03 dw02 dw01 ieee gtech"),
-          ("dw04","dw04 ieee dw01 dware gtech"),
-          ("dw05","dw05 ieee dware"),
-          ("dw06","dw06 ieee dware"),
-          ("dw07","ieee dware"),
-          ("dware","ieee dware"),
-          ("gtech","ieee gtech"),
-          ("ramlib","std ieee"),
-          ("std_cell_lib","ieee std_cell_lib"),
-          ("synopsys",[])]
-
+depLibs =
+  [ ( "des_system_lib"
+    , "std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee")
+  , ("dw01", "ieee dw01 dware gtech")
+  , ("dw02", "ieee dw02 dware")
+  , ("dw03", "std synopsys dware dw03 dw02 dw01 ieee gtech")
+  , ("dw04", "dw04 ieee dw01 dware gtech")
+  , ("dw05", "dw05 ieee dware")
+  , ("dw06", "dw06 ieee dware")
+  , ("dw07", "ieee dware")
+  , ("dware", "ieee dware")
+  , ("gtech", "ieee gtech")
+  , ("ramlib", "std ieee")
+  , ("std_cell_lib", "ieee std_cell_lib")
+  , ("synopsys", [])
+  ]
 
+toposort :: [(String, String)] -> [String]
 toposort xs
-      | (not.null) cycleDetect = error $ "Dependency cycle detected for libs " ++ show cycleDetect
-      | otherwise              = foldl makePrecede [] dB
+  | (not . null) cycleDetect =
+    error $ "Dependency cycle detected for libs " ++ show cycleDetect
+  | otherwise = foldl makePrecede [] dB
+  where
+    dB = ((\(x, y) -> (x, y \\ x)) . (return *** words)) <$> xs
+    makePrecede ts ([x], xs) =
+      nub $
+      case elemIndex x ts of
+        Just i -> uncurry (++) $ first (++ xs) $ splitAt i ts
+        _ -> ts ++ xs ++ [x]
+    cycleDetect =
+      filter ((> 1) . length) $
+      (\[(a, as), (b, bs)] -> (a `intersect` bs) ++ (b `intersect` as)) <$>
+      combs 2 dB
 
-   where dB = map ((\(x,y) -> (x,y \\ x)). (return *** words)) xs
-
-         makePrecede ts ([x],xs)  = nub $ case elemIndex x ts of
-                                          Just i  -> uncurry(++) $ first(++xs) $ splitAt i ts
-                                          _       -> ts ++ xs ++ [x]
-
-         cycleDetect = filter ((>1).length)
-                       $ map (\[(a,as), (b,bs)] -> (a `intersect` bs) ++ (b `intersect`as))
-                       $ combs 2 dB
+main :: IO ()
+main = print $ toposort depLibs