From 08d4c25e140431877ce473622f3705e7a05485bc Mon Sep 17 00:00:00 2001
From: "jeanphilippe.bernardy@gmail.com" <unknown>
Date: Sat, 10 Feb 2007 06:51:15 +0000
Subject: [PATCH] Fix the types of minView/maxView (ticket #1134)

---
 Data/Map.hs |   28 +++++++++++++++++++++-------
 Data/Set.hs |   11 ++++-------
 2 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/Data/Map.hs b/Data/Map.hs
index 1d812fc..0710a28 100644
--- a/Data/Map.hs
+++ b/Data/Map.hs
@@ -594,19 +594,33 @@ updateMaxWithKey f t
       Bin sx kx x l r    -> balance kx x l (updateMaxWithKey f r)
       Tip                -> Tip
 
--- | /O(log n)/. Retrieves the minimal key of the map, and the map stripped from that element
+-- | /O(log n)/. Retrieves the minimal (key,value) pair of the map, and the map stripped from that element
 -- @fail@s (in the monad) when passed an empty map.
-minView :: Monad m => Map k a -> m (Map k a, (k,a))
+minViewWithKey :: Monad m => Map k a -> m ((k,a), Map k a)
+minViewWithKey Tip = fail "Map.minView: empty map"
+minViewWithKey x = return (deleteFindMin x)
+
+-- | /O(log n)/. Retrieves the maximal (key,value) pair of the map, and the map stripped from that element
+-- @fail@s (in the monad) when passed an empty map.
+maxViewWithKey :: Monad m => Map k a -> m ((k,a), Map k a)
+maxViewWithKey Tip = fail "Map.maxView: empty map"
+maxViewWithKey x = return (deleteFindMax x)
+
+-- | /O(log n)/. Retrieves the minimal key\'s value of the map, and the map stripped from that element
+-- @fail@s (in the monad) when passed an empty map.
+minView :: Monad m => Map k a -> m (a, Map k a)
 minView Tip = fail "Map.minView: empty map"
-minView x = return (swap $ deleteFindMin x)
+minView x = return (first snd $ deleteFindMin x)
 
--- | /O(log n)/. Retrieves the maximal key of the map, and the map stripped from that element
+-- | /O(log n)/. Retrieves the maximal key\'s value of the map, and the map stripped from that element
 -- @fail@s (in the monad) when passed an empty map.
-maxView :: Monad m => Map k a -> m (Map k a, (k,a))
+maxView :: Monad m => Map k a -> m (a, Map k a)
 maxView Tip = fail "Map.maxView: empty map"
-maxView x = return (swap $ deleteFindMax x)
+maxView x = return (first snd $ deleteFindMax x)
 
-swap (a,b) = (b,a)
+-- Update the 1st component of a tuple (special case of Control.Arrow.first)
+first :: (a -> b) -> (a,c) -> (b,c)
+first f (x,y) = (f x, y)
 
 {--------------------------------------------------------------------
   Union. 
diff --git a/Data/Set.hs b/Data/Set.hs
index 5f45ce9..9ec9e4c 100644
--- a/Data/Set.hs
+++ b/Data/Set.hs
@@ -746,18 +746,15 @@ deleteFindMax t
 
 -- | /O(log n)/. Retrieves the minimal key of the set, and the set stripped from that element
 -- @fail@s (in the monad) when passed an empty set.
-minView :: Monad m => Set a -> m (Set a, a)
+minView :: Monad m => Set a -> m (a, Set a)
 minView Tip = fail "Set.minView: empty set"
-minView x = return (swap $ deleteFindMin x)
+minView x = return (deleteFindMin x)
 
 -- | /O(log n)/. Retrieves the maximal key of the set, and the set stripped from that element
 -- @fail@s (in the monad) when passed an empty set.
-maxView :: Monad m => Set a -> m (Set a, a)
+maxView :: Monad m => Set a -> m (a, Set a)
 maxView Tip = fail "Set.maxView: empty set"
-maxView x = return (swap $ deleteFindMax x)
-
-swap (a,b) = (b,a)
-
+maxView x = return (deleteFindMax x)
 
 
 {--------------------------------------------------------------------
-- 
1.7.10.4