[commit: packages/containers] cleaned_bugfix394, master, merge-doc-target, merge-fixes-5.9, merge-restrict-fix-5.8, revert-408-bugfix_394: Add alterF for Data.IntMap (e04d19c)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/containers

On branches: cleaned_bugfix394,master,merge-doc-target,merge-fixes-5.9,merge-restrict-fix-5.8,revert-408-bugfix_394
Link       : http://git.haskell.org/packages/containers.git/commitdiff/e04d19c29532757d4880f72a74cf676c43ffaaaf

>---------------------------------------------------------------

commit e04d19c29532757d4880f72a74cf676c43ffaaaf
Author: David Feuer <David.Feuer at gmail.com>
Date:   Wed May 25 03:17:14 2016 -0400

    Add alterF for Data.IntMap
    
    The implementation is just taken from `Control.Lens.At`, because
    `IntMap` lookup is so fast there's no point in trying to be clever
    about it.
    
    Clear up unused-binding warning in `Data.Sequence`.


>---------------------------------------------------------------

e04d19c29532757d4880f72a74cf676c43ffaaaf
 Data/IntMap/Base.hs   | 37 +++++++++++++++++++++++++++++++++++++
 Data/IntMap/Lazy.hs   |  1 +
 Data/IntMap/Strict.hs | 41 +++++++++++++++++++++++++++++++++++++++++
 Data/Sequence.hs      |  2 +-
 changelog.md          |  2 +-
 5 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/Data/IntMap/Base.hs b/Data/IntMap/Base.hs
index 6a4c0dc..a585328 100644
--- a/Data/IntMap/Base.hs
+++ b/Data/IntMap/Base.hs
@@ -90,6 +90,7 @@ module Data.IntMap.Base (
     , updateWithKey
     , updateLookupWithKey
     , alter
+    , alterF
 
     -- * Combine
 
@@ -835,6 +836,42 @@ alter f k Nil     = case f Nothing of
                       Just x -> Tip k x
                       Nothing -> Nil
 
+-- | /O(log n)/. The expression (@'alterF' f k map@) alters the value @x@ at
+-- @k@, or absence thereof.  'alterF' can be used to inspect, insert, delete,
+-- or update a value in an 'IntMap'.  In short : @'lookup' k <$> 'alterF' f k m = f
+-- ('lookup' k m)@.
+--
+-- Example:
+--
+-- @
+-- interactiveAlter :: Int -> IntMap String -> IO (IntMap String)
+-- interactiveAlter k m = alterF f k m where
+--   f Nothing -> do
+--      putStrLn $ show k ++
+--          " was not found in the map. Would you like to add it?"
+--      getUserResponse1 :: IO (Maybe String)
+--   f (Just old) -> do
+--      putStrLn "The key is currently bound to " ++ show old ++
+--          ". Would you like to change or delete it?"
+--      getUserresponse2 :: IO (Maybe String)
+-- @
+--
+-- 'alterF' is the most general operation for working with an individual
+-- key that may or may not be in a given map.
+--
+-- Note: 'alterF' is a flipped version of the 'at' combinator from
+-- 'Control.Lens.At'.
+--
+-- @since 0.5.8
+
+alterF :: Functor f
+       => (Maybe a -> f (Maybe a)) -> Key -> IntMap a -> f (IntMap a)
+-- This implementation was stolen from 'Control.Lens.At'.
+alterF f k m = (<$> f mv) $ \fres ->
+  case fres of
+    Nothing -> maybe m (const (delete k m)) mv
+    Just v' -> insert k v' m
+  where mv = lookup k m
 
 {--------------------------------------------------------------------
   Union
diff --git a/Data/IntMap/Lazy.hs b/Data/IntMap/Lazy.hs
index d3c0c1d..8283017 100644
--- a/Data/IntMap/Lazy.hs
+++ b/Data/IntMap/Lazy.hs
@@ -96,6 +96,7 @@ module Data.IntMap.Lazy (
     , updateWithKey
     , updateLookupWithKey
     , alter
+    , alterF
 
     -- * Combine
 
diff --git a/Data/IntMap/Strict.hs b/Data/IntMap/Strict.hs
index 64fdd9d..b084d01 100644
--- a/Data/IntMap/Strict.hs
+++ b/Data/IntMap/Strict.hs
@@ -228,6 +228,7 @@ import Data.IntMap.Base hiding
     , updateWithKey
     , updateLookupWithKey
     , alter
+    , alterF
     , unionsWith
     , unionWith
     , unionWithKey
@@ -267,6 +268,9 @@ import Data.Utils.StrictPair
 #if __GLASGOW_HASKELL__ >= 709
 import Data.Coerce
 #endif
+#if !MIN_VERSION_base(4,8,0)
+import Data.Functor((<$>))
+#endif
 
 -- $strictness
 --
@@ -537,6 +541,43 @@ alter f !k t =
                            Just !x -> Tip k x
                            Nothing -> Nil
 
+-- | /O(log n)/. The expression (@'alterF' f k map@) alters the value @x@ at
+-- @k@, or absence thereof.  'alterF' can be used to inspect, insert, delete,
+-- or update a value in an 'IntMap'.  In short : @'lookup' k <$> 'alterF' f k m = f
+-- ('lookup' k m)@.
+--
+-- Example:
+--
+-- @
+-- interactiveAlter :: Int -> IntMap String -> IO (IntMap String)
+-- interactiveAlter k m = alterF f k m where
+--   f Nothing -> do
+--      putStrLn $ show k ++
+--          " was not found in the map. Would you like to add it?"
+--      getUserResponse1 :: IO (Maybe String)
+--   f (Just old) -> do
+--      putStrLn "The key is currently bound to " ++ show old ++
+--          ". Would you like to change or delete it?"
+--      getUserresponse2 :: IO (Maybe String)
+-- @
+--
+-- 'alterF' is the most general operation for working with an individual
+-- key that may or may not be in a given map.
+
+-- Note: 'alterF' is a flipped version of the 'at' combinator from
+-- 'Control.Lens.At'.
+--
+-- @since 0.5.8
+
+alterF :: Functor f
+       => (Maybe a -> f (Maybe a)) -> Key -> IntMap a -> f (IntMap a)
+-- This implementation was modified from 'Control.Lens.At'.
+alterF f k m = (<$> f mv) $ \fres ->
+  case fres of
+    Nothing -> maybe m (const (delete k m)) mv
+    Just !v' -> insert k v' m
+  where mv = lookup k m
+
 
 {--------------------------------------------------------------------
   Union
diff --git a/Data/Sequence.hs b/Data/Sequence.hs
index 46ae543..85d255c 100644
--- a/Data/Sequence.hs
+++ b/Data/Sequence.hs
@@ -1047,7 +1047,7 @@ replicateM n x
 -- @since 0.5.8
 cycleN :: Int -> Seq a -> Seq a
 cycleN n !_xs | n < 0 = error "cycleN takes a non-negative argument"
-cycleN n xs   | null xs = error "cycleN takes a non-empty sequence"
+cycleN _n xs  | null xs = error "cycleN takes a non-empty sequence"
 cycleN n xs = cycleNTimes reps xs >< take final xs
   where
     (reps, final) = n `quotRem` length xs
diff --git a/changelog.md b/changelog.md
index af5f88c..2b889b5 100644
--- a/changelog.md
+++ b/changelog.md
@@ -15,7 +15,7 @@
   * Use `BangPatterns` throughout to reduce noise. This extension
     is now *required* to compile `containers`.
 
-  * Add `alterF` for `Data.Map`.
+  * Add `alterF` for `Data.Map` and `Data.IntMap`.
 
   * Make `Data.Map.Strict.traverseWithKey` force result values before
     installing them in the new map.