{-# OPTIONS -cpp -fglasgow-exts -fno-bang-patterns #-}
-----------------------------------------------------------------------------
+-- |
-- Module : Data.IntMap
-- Copyright : (c) Daan Leijen 2002
-- License : BSD-style
--
-- An efficient implementation of maps from integer keys to values.
--
--- This module is intended to be imported @qualified@, to avoid name
--- clashes with "Prelude" functions. eg.
+-- Since many function names (but not the type name) clash with
+-- "Prelude" names, this module is usually imported @qualified@, e.g.
--
--- > import Data.IntMap as Map
+-- > import Data.IntMap (IntMap)
+-- > import qualified Data.IntMap as IntMap
--
-- The implementation is based on /big-endian patricia trees/. This data
-- structure performs especially well on binary operations like 'union'
, null
, size
, member
+ , notMember
, lookup
, findWithDefault
, update
, updateWithKey
, updateLookupWithKey
+ , alter
-- * Combine
, partition
, partitionWithKey
+ , mapMaybe
+ , mapMaybeWithKey
+ , mapEither
+ , mapEitherWithKey
+
, split
, splitLookup
Nothing -> False
Just x -> True
+-- | /O(log n)/. Is the key not a member of the map?
+notMember :: Key -> IntMap a -> Bool
+notMember k m = not $ member k m
+
-- | /O(min(n,W))/. Lookup the value at a key in the map.
-lookup :: Key -> IntMap a -> Maybe a
-lookup k t
+lookup :: (Monad m) => Key -> IntMap a -> m a
+lookup k t = case lookup' k t of
+ Just x -> return x
+ Nothing -> fail "Data.IntMap.lookup: Key not found"
+
+lookup' :: Key -> IntMap a -> Maybe a
+lookup' k t
= let nk = natFromInt k in seq nk (lookupN nk t)
lookupN :: Nat -> IntMap a -> Maybe a
Nil -> (Nothing,Nil)
+
+-- | /O(log n)/. The expression (@'alter' f k map@) alters the value @x@ at @k@, or absence thereof.
+-- 'alter' can be used to insert, delete, or update a value in a 'Map'.
+-- In short : @'lookup' k ('alter' f k m) = f ('lookup' k m)@
+alter f k t
+ = case t of
+ Bin p m l r
+ | nomatch k p m -> case f Nothing of
+ Nothing -> t
+ Just x -> join k (Tip k x) p t
+ | zero k m -> bin p m (alter f k l) r
+ | otherwise -> bin p m l (alter f k r)
+ Tip ky y
+ | k==ky -> case f (Just y) of
+ Just x -> Tip ky x
+ Nothing -> Nil
+ | otherwise -> case f Nothing of
+ Just x -> join k (Tip k x) ky t
+ Nothing -> Tip ky y
+ Nil -> case f Nothing of
+ Just x -> Tip k x
+ Nothing -> Nil
+
+
{--------------------------------------------------------------------
Union
--------------------------------------------------------------------}
| otherwise -> (Nil,t)
Nil -> (Nil,Nil)
+-- | /O(n)/. Map values and collect the 'Just' results.
+mapMaybe :: (a -> Maybe b) -> IntMap a -> IntMap b
+mapMaybe f m
+ = mapMaybeWithKey (\k x -> f x) m
+
+-- | /O(n)/. Map keys\/values and collect the 'Just' results.
+mapMaybeWithKey :: (Key -> a -> Maybe b) -> IntMap a -> IntMap b
+mapMaybeWithKey f (Bin p m l r)
+ = bin p m (mapMaybeWithKey f l) (mapMaybeWithKey f r)
+mapMaybeWithKey f (Tip k x) = case f k x of
+ Just y -> Tip k y
+ Nothing -> Nil
+mapMaybeWithKey f Nil = Nil
+
+-- | /O(n)/. Map values and separate the 'Left' and 'Right' results.
+mapEither :: (a -> Either b c) -> IntMap a -> (IntMap b, IntMap c)
+mapEither f m
+ = mapEitherWithKey (\k x -> f x) m
+
+-- | /O(n)/. Map keys\/values and separate the 'Left' and 'Right' results.
+mapEitherWithKey :: (Key -> a -> Either b c) -> IntMap a -> (IntMap b, IntMap c)
+mapEitherWithKey f (Bin p m l r)
+ = (bin p m l1 r1, bin p m l2 r2)
+ where
+ (l1,l2) = mapEitherWithKey f l
+ (r1,r2) = mapEitherWithKey f r
+mapEitherWithKey f (Tip k x) = case f k x of
+ Left y -> (Tip k y, Nil)
+ Right z -> (Nil, Tip k z)
+mapEitherWithKey f Nil = (Nil, Nil)
-- | /O(log n)/. The expression (@'split' k map@) is a pair @(map1,map2)@
-- where all keys in @map1@ are lower than @k@ and all keys in