add Control.Monad.Instances to nhc98 build

[haskell-directory.git] / Data / IntMap.hs

diff --git a/Data/IntMap.hs b/Data/IntMap.hs
index 652a23e..e4377e5 100644 (file)
--- a/Data/IntMap.hs
+++ b/Data/IntMap.hs
@@ -1,5 +1,6 @@
 {-# OPTIONS -cpp -fglasgow-exts -fno-bang-patterns #-} 
 -----------------------------------------------------------------------------
+-- |
 -- Module      :  Data.IntMap
 -- Copyright   :  (c) Daan Leijen 2002
 -- License     :  BSD-style
@@ -9,10 +10,11 @@
 --
 -- 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'
@@ -121,6 +123,11 @@ module Data.IntMap  (
             , partition
             , partitionWithKey
 
+            , mapMaybe
+            , mapMaybeWithKey
+            , mapEither
+            , mapEitherWithKey
+
             , split         
             , splitLookup   
 
@@ -847,6 +854,36 @@ partitionWithKey pred t
         | 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