2 files changed, 8 insertions, 7 deletions

diff --git a/execs/Day07.hs b/execs/Day07.hs
index 1587e2b..72043af 100644
--- a/execs/Day07.hs
+++ b/execs/Day07.hs
@@ -2,6 +2,7 @@ module Main where
 
 import           Data.Map (Map)
 import qualified Data.Map as Map
+import           Utils
 
 myBag = "shiny gold"
 
@@ -19,18 +20,14 @@ parseLine s = (leadingBag, contained)
 
 canContain :: Map String [(Int, String)] -> String -> Bool
 canContain m outer = myBag `elem` inners || any (canContain m) inners
-    where (Just inners) = map snd <$> Map.lookup outer m
+    where inners = map snd $ m Map.! outer
 
 countNested :: String -> Map String [(Int, String)] -> Int
-countNested s m = if null l
-                     then 0
-                     else sum $ map counter l
-    where (Just l) = Map.lookup s m
-          counter (count, bag) = count + count * countNested bag m
+countNested s m = foldl (\acc (c,b) -> acc + c * (1 + countNested b m)) 0 $ m Map.! s
 
 main :: IO ()
 main = do
     n <- map (parseLine . words) . lines <$> readFile "input/07"
     let q = Map.fromList n
-    print $ length $ filter (== True) $ map (canContain q . fst) $ Map.toList q
+    print $ howMany (canContain q . fst) $ Map.toList q
     print $ countNested myBag q
diff --git a/lib/Utils.hs b/lib/Utils.hs
index 1eb42fc..4c9a581 100644
--- a/lib/Utils.hs
+++ b/lib/Utils.hs
@@ -4,6 +4,7 @@ module Utils ( binaryToInt
              , right
              , bet
              , (&+)
+             , howMany
              ) where 
 
 import Data.Char (digitToInt)
@@ -30,3 +31,6 @@ bet k (l, u) = k >= l && k <= u
 -- combine filter predicates
 (&+) :: (a -> Bool) -> (a -> Bool) -> (a -> Bool)
 (&+) = liftM2 (&&)
+
+howMany :: (a -> Bool) -> [a] -> Int
+howMany predicate = length . filter ((== True) . predicate)