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-rw-r--r--StackSet.hs65
1 files changed, 25 insertions, 40 deletions
diff --git a/StackSet.hs b/StackSet.hs
index c15665d..c79ea13 100644
--- a/StackSet.hs
+++ b/StackSet.hs
@@ -21,32 +21,25 @@
module StackSet (
- StackSet, -- abstract
+ StackSet, -- abstract, deriving Show,Eq
-- * Introduction
empty, -- :: Int -> StackSet a
- fromList, -- :: [[a]] -> StackSet a
- toList, -- :: StackSet -> [[a]]
+ fromList, -- :: Ord a => (Int,[[a]]) -> StackSet a
+ toList, -- :: StackSet a -> (Int,[[a]])
-- * Inspection
- size, -- :: StackSet -> Int
- member, -- :: Ord a => a -> StackSet a -> Bool
+ size, -- :: StackSet a -> Int
peek, -- :: StackSet a -> Maybe a
- stack, -- :: StackSet a -> [a]
- cursor, -- :: StackSet a -> Int
- index, -- :: StackSet a -> Int -> Maybe [a]
+ index, -- :: Int -> StackSet a -> Maybe [a]
+ member, -- :: Ord a => a -> StackSet a -> Bool
+ current, -- :: StackSet a -> Int
- -- * Modification to the current stack
+ -- * Modification
push, -- :: Ord a => a -> StackSet a -> StackSet a
- pop, -- :: Ord a => StackSet a -> StackSet a
rotate, -- :: Ordering -> StackSet a -> StackSet a
shift, -- :: Ord a => Int -> StackSet a -> StackSet a
-
- -- * Modification to arbitrary stacks
delete, -- :: Ord a => a -> StackSet a -> StackSet a
- insert, -- :: Ord a => a -> Int -> StackSet a -> StackSet a
-
- -- * Changing which stack is 'current'
view, -- :: Int -> StackSet a -> StackSet a
) where
@@ -59,16 +52,17 @@ import qualified Data.Sequence as S
------------------------------------------------------------------------
--- | The StackSet data structure. A table of stacks, with a cursor
+-- | The StackSet data structure. A table of stacks, with a current pointer
data StackSet a =
StackSet
- { cursor :: {-# UNPACK #-} !Int -- ^ the currently visible stack
+ { current:: {-# UNPACK #-} !Int -- ^ the currently visible stack
, size :: {-# UNPACK #-} !Int -- ^ size of the stack list
, stacks :: {-# UNPACK #-} !(S.Seq [a]) -- ^ the separate stacks
, cache :: {-# UNPACK #-} !(M.Map a Int) -- ^ a cache of windows back to their stacks
} deriving Eq
-instance Show a => Show (StackSet a) where show = show . toList
+instance Show a => Show (StackSet a) where
+ showsPrec p s r = showsPrec p (show . toList $ s) r
-- Ord a constraint on 'a' as we use it as a key.
--
@@ -83,7 +77,7 @@ instance Show a => Show (StackSet a) where show = show . toList
-- | Create a new empty stacks of size 'n', indexed from 0. The
-- 0-indexed stack will be current.
empty :: Int -> StackSet a
-empty n = StackSet { cursor = 0
+empty n = StackSet { current= 0
, size = n -- constant
, stacks = S.fromList (replicate n [])
, cache = M.empty
@@ -112,7 +106,7 @@ fromList (o,xs) = view o $
-- | toList. Flatten a stackset to a list of lists
toList :: StackSet a -> (Int,[[a]])
-toList x = (cursor x, F.toList (stacks x))
+toList x = (current x, F.toList (stacks x))
------------------------------------------------------------------------
@@ -121,33 +115,19 @@ toList x = (cursor x, F.toList (stacks x))
-- If the element is managed on another stack, it is removed from that
-- stack first.
push :: Ord a => a -> StackSet a -> StackSet a
-push k w = insert k (cursor w) w
-
--- | Pop. Pop the element off the top of the stack and discard it.
--- A new StackSet is returned. If the current stack is empty, the
--- original StackSet is returned unchanged.
-pop :: Ord a => StackSet a -> StackSet a
-pop w = case peek w of
- Nothing -> w
- Just t -> delete t w
+push k w = insert k (current w) w
-- | Extract the element on the top of the current stack. If no such
-- element exists, Nothing is returned.
peek :: StackSet a -> Maybe a
-peek = listToMaybe . stack
+peek w = listToMaybe . fromJust $ index (current w) w
-- | Index. Extract stack at index 'n'. If the index is invalid,
-- Nothing is returned.
-index :: StackSet a -> Int -> Maybe [a]
-index w n | n < 0 || n >= size w = Nothing
+index :: Int -> StackSet a -> Maybe [a]
+index n w | n < 0 || n >= size w = Nothing
| otherwise = Just (stacks w `S.index` n)
--- | Return the current stack
-stack :: StackSet a -> [a]
-stack w = case index w (cursor w) of
- Just s -> s
- Nothing -> error $ "current: no 'current' stack in StackSet: " ++ show (cursor w) -- can't happen
-
-- | rotate. cycle the current window list up or down.
--
-- rotate EQ --> [5,6,7,8,1,2,3,4]
@@ -171,7 +151,7 @@ rotate o = unsafeModify rot -- safe, since 'rot' is guaranteed to only permute t
-- current StackSet. If the index is out of range, the original
-- StackSet is returned. StackSet are indexed from 0.
view :: Int -> StackSet a -> StackSet a
-view n w | n >= 0 && n < size w = w { cursor = n }
+view n w | n >= 0 && n < size w = w { current = n }
| otherwise = w
-- | shift. move the client on top of the current stack to the top of stack 'n'.
@@ -217,5 +197,10 @@ delete k w = case M.lookup k (cache w) of
-- and must not add or remove elements, or duplicate elements.
--
unsafeModify :: ([a] -> [a]) -> StackSet a -> StackSet a
-unsafeModify f w = w { stacks = S.adjust f (cursor w) (stacks w) }
+unsafeModify f w = w { stacks = S.adjust f (current w) (stacks w) }
+-- | Pop. Pop the element off the top of the stack and discard it.
+-- A new StackSet is returned. If the current stack is empty, the
+-- original StackSet is returned unchanged.
+pop :: Ord a => StackSet a -> StackSet a
+pop w = maybe w (flip delete w) (peek w)