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simpler type (no need to cache size, we *could* grow new stacks on demand now)
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74
StackSet.hs
74
StackSet.hs
@@ -19,33 +19,10 @@
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-- may be on only 1 screen at any given time.
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--
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module StackSet (
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StackSet, -- abstract, deriving Show,Eq
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-- * Introduction
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empty, -- :: Int -> StackSet a
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fromList, -- :: Ord a => (Int,[[a]]) -> StackSet a
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toList, -- :: StackSet a -> (Int,[[a]])
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-- * Inspection
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size, -- :: StackSet a -> Int
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peek, -- :: StackSet a -> Maybe a
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index, -- :: Int -> StackSet a -> [a]
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member, -- :: Ord a => a -> StackSet a -> Bool
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current, -- :: StackSet a -> Int
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-- * Modification
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push, -- :: Ord a => a -> StackSet a -> StackSet a
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rotate, -- :: Ordering -> StackSet a -> StackSet a
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shift, -- :: Ord a => Int -> StackSet a -> StackSet a
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delete, -- :: Ord a => a -> StackSet a -> StackSet a
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view, -- :: Int -> StackSet a -> StackSet a
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) where
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module StackSet {- everything -} where
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import Data.Maybe
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import qualified Data.List as L
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import qualified Data.List as L (nub,delete)
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import qualified Data.Map as M
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import qualified Data.IntMap as I
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@@ -55,7 +32,6 @@ import qualified Data.IntMap as I
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data StackSet a =
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StackSet
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{ current:: {-# UNPACK #-} !Int -- ^ the currently visible stack
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, size :: {-# UNPACK #-} !Int -- ^ size of the stack list
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, stacks :: {-# UNPACK #-} !(I.IntMap [a]) -- ^ the separate stacks
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, cache :: {-# UNPACK #-} !(M.Map a Int) -- ^ a cache of windows back to their stacks
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} deriving Eq
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@@ -67,48 +43,42 @@ instance Show a => Show (StackSet a) where
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--
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-- The cache is used to check on insertion that we don't already have
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-- this window managed on another stack
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--
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-- Currently stacks are of a fixed size. There's no firm reason to
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-- do this (new empty stacks could be created on the fly).
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------------------------------------------------------------------------
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-- | /O(n)/. Create a new empty stacks of size 'n', indexed from 0. The
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-- 0-indexed stack will be current.
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empty :: Int -> StackSet a
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empty n = StackSet { current= 0
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, size = n -- constant
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, stacks = I.fromList (zip [0..n-1] (repeat []))
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, cache = M.empty
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}
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empty n = StackSet { current = 0
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, stacks = I.fromList (zip [0..n-1] (repeat []))
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, cache = M.empty }
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-- | /O(log w)/. True if x is somewhere in the StackSet
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member :: Ord a => a -> StackSet a -> Bool
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member a w = M.member a (cache w)
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-- | /O(n)/. Number of stacks
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size :: StackSet a -> Int
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size = I.size . stacks
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------------------------------------------------------------------------
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-- | fromList. Build a new StackSet from a list of list of elements
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-- If there are duplicates in the list, the last occurence wins.
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fromList :: Ord a => (Int,[[a]]) -> StackSet a
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fromList (_,[])
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= error "Cannot build a StackSet from an empty list"
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fromList (_,[]) = error "Cannot build a StackSet from an empty list"
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fromList (n,xs)
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| n < 0 || n >= length xs
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= error $ "Cursor index is out of range: " ++ show (n, length xs)
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fromList (n,xs) | n < 0 || n >= length xs
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= error $ "Cursor index is out of range: " ++ show (n, length xs)
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fromList (o,xs) = view o $
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foldr (\(i,ys) s ->
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foldr (\a t -> insert a i t) s ys)
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(empty (length xs)) (zip [0..] xs)
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fromList (o,xs) = view o $ foldr (\(i,ys) s ->
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foldr (\a t -> insert a i t) s ys)
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(empty (length xs)) (zip [0..] xs)
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-- | toList. Flatten a stackset to a list of lists
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toList :: StackSet a -> (Int,[[a]])
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toList x = (current x, map snd $ I.toList (stacks x))
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------------------------------------------------------------------------
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-- | Push. Insert an element onto the top of the current stack.
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-- If the element is already in the current stack, it is moved to the top.
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-- If the element is managed on another stack, it is removed from that
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@@ -129,8 +99,8 @@ index k w = fromJust (I.lookup k (stacks w))
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-- | /O(1)/. view. Set the stack specified by the Int argument as being the
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-- current StackSet. If the index is out of range an exception is thrown.
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view :: Int -> StackSet a -> StackSet a
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view n w | n >= 0 && n < size w = w { current = n }
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| otherwise = error $ "view: index out of bounds: " ++ show n
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view n w | n >= 0 && n < I.size (stacks w) = w { current = n }
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| otherwise = error $ "view: index out of bounds: " ++ show n
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-- | /O(log n)/. rotate. cycle the current window list up or down.
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--
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@@ -142,12 +112,10 @@ view n w | n >= 0 && n < size w = w { current = n }
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--
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rotate :: Ordering -> StackSet a -> StackSet a
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rotate o w = w { stacks = I.adjust rot (current w) (stacks w) }
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where
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rot s = take l . drop offset . cycle $ s
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where
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n = fromEnum o - 1
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l = length s
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offset = if n < 0 then l + n else n
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where rot s = take l . drop offset . cycle $ s
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where n = fromEnum o - 1
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l = length s
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offset = if n < 0 then l + n else n
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-- | /O(log n)/. shift. move the client on top of the current stack to
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-- the top of stack 'n'. If the stack to move to is not valid, and
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