Add a couple of functions to BDict

1 files changed, 17 insertions, 0 deletions

diff --git a/src/Data/BEncode/BDict.hs b/src/Data/BEncode/BDict.hs
index 4ff5caa..d1d5215 100644
--- a/src/Data/BEncode/BDict.hs
+++ b/src/Data/BEncode/BDict.hs
@@ -17,6 +17,8 @@ module Data.BEncode.BDict
        , Data.BEncode.BDict.singleton
 
          -- * Query
+       , Data.BEncode.BDict.null
+       , Data.BEncode.BDict.member
        , Data.BEncode.BDict.lookup
 
          -- * Combine
@@ -81,6 +83,21 @@ singleton :: BKey -> a -> BDictMap a
 singleton k v = Cons k v Nil
 {-# INLINE singleton #-}
 
+-- | /O(1)/. Is the dictionary empty?
+null :: BDictMap a -> Bool
+null Nil = True
+null _   = False
+{-# INLINE null #-}
+
+-- | /O(n)/. Is the key a member of the dictionary?
+member :: BKey -> BDictMap a -> Bool
+member key = go
+  where
+    go  Nil          = False
+    go (Cons k _ xs)
+      | k == key  = True
+      | otherwise = go xs
+
 -- | /O(n)/. Lookup the value at a key in the dictionary.
 lookup :: BKey -> BDictMap a -> Maybe a
 lookup x = go