Implement keys

Data/CritBit/Tree.hs

@@ -88,7 +88,7 @@ module Data.CritBit.Tree
 
     -- * Conversion
     -- , elems
-    -- , keys
+    , keys
     -- , assocs
     -- , keysSet
     -- , fromSet
@@ -500,6 +500,14 @@ foldrWithKeyWith maybeSeq f z0 (CritBit root) = go root z0
     go Empty z                     = z
 {-# INLINE foldrWithKeyWith #-}
 
+-- | /O(n)/. Return all keys of the map in ascending order.
+--
+-- > keys (fromList [("b",5), ("a",3)]) == ["a","b"]
+-- > keys empty == []
+keys :: CritBit k v -> [k]
+keys m = foldrWithKey f [] m
+  where f k _ ks = k : ks
+
 unionL :: (CritBitKey k) => CritBit k v -> CritBit k v -> CritBit k v
 unionL a b = foldlWithKey' (\m k v -> insert k v m) b a
 {-# INLINABLE unionL #-}

benchmarks/Benchmarks.hs

@@ -176,6 +176,7 @@ main = do
                                     (H.foldlWithKey' f 0) id
       , bgroup "foldl'" $ function whnf (C.foldl' (+) 0) (Map.foldl' (+) 0)
                           (H.foldl' (+) 0) id
+      , bgroup "keys" $ function nf C.keys Map.keys H.keys Trie.keys
       , bgroup "union" $ twoMaps C.unionR Map.union H.union Trie.unionR
       ]
     , bgroup "text" [

tests/Properties.hs

@@ -105,6 +105,9 @@ t_foldlWithKey' _ (KV kvs) =
   where
     f (l,s) k v = (k:l,s+v)
 
+t_keys :: (CritBitKey k, Ord k) => k -> KV k -> Bool
+t_keys _ (KV kvs) = C.keys (C.fromList kvs) == Map.keys (Map.fromList kvs)
+
 propertiesFor :: (Arbitrary k, CritBitKey k, Ord k, Show k) => k -> [Test]
 propertiesFor t = [
     testProperty "t_fromList_toList" $ t_fromList_toList t
@@ -118,6 +121,7 @@ propertiesFor t = [
   , testProperty "t_foldlWithKey" $ t_foldlWithKey t
   , testProperty "t_foldl'" $ t_foldl' t
   , testProperty "t_foldlWithKey'" $ t_foldlWithKey' t
+  , testProperty "t_keys" $ t_keys t
   ]
 
 properties :: [Test]