data-clist (empty) → 0.0.1

raw patch · 4 files changed

+414/−0 lines, 4 filesdep +QuickCheckdep +basesetup-changed

Dependencies added: QuickCheck, base

Files

• LICENSE +165/−0
• Setup.hs +4/−0
• data-clist.cabal +27/−0
• src/Data/CircularList.hs +218/−0

@@ -0,0 +1,165 @@+		   GNU LESSER GENERAL PUBLIC LICENSE+                       Version 3, 29 June 2007++ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>+ Everyone is permitted to copy and distribute verbatim copies+ of this license document, but changing it is not allowed.+++  This version of the GNU Lesser General Public License incorporates+the terms and conditions of version 3 of the GNU General Public+License, supplemented by the additional permissions listed below.++  0. 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@@ -0,0 +1,4 @@+module Main where++import Distribution.Simple+main = defaultMain

@@ -0,0 +1,27 @@+Name: data-clist+Synopsis: Simple functional ring type.+Description: Simple functional bidirectional ring type.++             Given that the ring terminiology+             clashes with certain mathematical branches, we're using the term+             CList or CircularList instead.+Version: 0.0.1+License: LGPL+License-File: LICENSE+Author: John Van Enk <vanenkj@gmail.com>+Maintainer: John Van Enk <vanenkj@gmail.com>+Stability: experimental+Category: Data Structures+Cabal-Version: >= 1.6+Build-Type: Simple+Package-URL: http://github.com/sw17ch/data-ring++Library+    Build-Depends: base >= 4 && < 5,+                   QuickCheck >= 2.1 && < 2.2++    Exposed-Modules:+        Data.CircularList++    ghc-options:        -Wall+    hs-source-dirs:     src

@@ -0,0 +1,218 @@+{- |+A simple purely functional circular list, or ring, data type.++Lets describe what we mean by 'ring'. A ring is a circular data structure+such that if you continue rotating the ring, you'll eventually return to+the element you first observed.++All of our analogies involve sitting at a table who's top surface rotates+about its center axis (think of those convenient rotating platforms one+often finds in an (Americanized) Chinese Restaurant).++Only the closest item on the table is avialable to us. In order to reach+other elements on the table, we need to rotate the table to the left or +the right.++Our convention for this problem says that rotations to the right are a+forward motion while rotations to the left are backward motions.++We'll use the following circular list for our examples:++>   8 7 6+>  9     5+> A       4+> B       3+>  C     2+>   D 0 1+>     ^++The pointer at the bottom represents our position at the table. The element+currently in front of is is referred to as the `focus`. So, in this case, our+focus is 0.++If we were to rotate the table to the right using the `rotR` operation, we'd+have the following table.++>   9 8 7+>  A     6+> B       5+> C       4+>  D     3+>   0 1 2+>     ^++This yeilds 1 as our new focus. Rotating this table left would return 0 to the+focus position.++-}+module Data.CircularList (+    -- * Data Types+    CList,+    -- * Functions+    -- ** Creation of CLists+    empty, fromList,+    -- ** Converting CLists to Lists+    leftElements, rightElements, toList, toInfList,+    -- ** Extraction and Accumulation+    focus, insertL, insertR,+    removeL, removeR,+    -- ** Manipulation of Focus+    rotR, rotL,+    -- ** Manipulation of Packing+    balance, packL, packR,+    -- ** Information+    isEmpty, size,+) where++import Test.QuickCheck.Arbitrary+import Test.QuickCheck.Gen++-- | A functional ring type.+data CList a = Empty+             | CList [a] a [a]+    deriving (Eq)++{- Creating CLists -}++-- | An empty CList.+empty :: CList a+empty = Empty++-- |Make a (balanced) CList from a list.+fromList :: [a] -> CList a+fromList [] = Empty+fromList a@(i:is) = let len = length a+                        (r,l) = splitAt (len `div` 2) is+                    in CList (reverse l) i r++{- Creating Lists -}++-- |Starting with the focus, go left and accumulate all+-- elements of the CList in a list.+leftElements :: CList a -> [a]+leftElements Empty = []+leftElements (CList l f r) = f : (l ++ (reverse r))++-- |Starting with the focus, go right and accumulate all+-- elements of the CList in a list.+rightElements :: CList a -> [a]+rightElements Empty = []+rightElements (CList l f r) = f : (r ++ (reverse l))++-- |Make a list from a CList.+toList :: CList a -> [a]+toList = rightElements++-- |Make a CList into an infinite list.+toInfList :: CList a -> [a]+toInfList = cycle . toList++{- Extraction and Accumulation -}++-- |Return the focus of the CList.+focus :: CList a -> Maybe a+focus Empty = Nothing+focus (CList _ f _) = Just f++-- |Insert an element into the CList as the new focus. The+-- old focus is now the next element to the right.+insertR :: a -> CList a -> CList a+insertR i Empty = CList [] i []+insertR i (CList l f r) = CList l i (f:r)++-- |Insert an element into the CList as the new focus. The+-- old focus is now the next element to the left.+insertL :: a -> CList a -> CList a+insertL i Empty = CList [] i []+insertL i (CList l f r) = CList (f:l) i r++-- |Remove the focus from the CList. The new focus is the+-- next element to the left.+removeL :: CList a -> CList a+removeL Empty = Empty+removeL (CList [] _ []) = Empty+removeL (CList (l:ls) _ rs) = CList ls l rs+removeL (CList [] _ rs) = let (f:ls) = reverse rs+                          in CList ls f [] ++-- |Remove the focus from the CList.+removeR :: CList a -> CList a+removeR Empty = Empty+removeR (CList [] _ []) = Empty+removeR (CList l _ (r:rs)) = CList l r rs+removeR (CList l _ []) = let (f:rs) = reverse l+                         in CList [] f rs++{- Manipulating Rotation -}++-- |Rotate the focus to the previous (left) element.+rotL :: CList a -> CList a+rotL Empty = Empty+rotL r@(CList [] _ []) = r+rotL (CList (l:ls) f rs) = CList ls l (f:rs)+rotL (CList [] f rs) = let (l:ls) = reverse rs+                       in CList ls l [f]++-- |Rotate the focus to the next (right) element.+rotR :: CList a -> CList a+rotR Empty = Empty+rotR r@(CList [] _ []) = r+rotR (CList ls f (r:rs)) = CList (f:ls) r rs+rotR (CList ls f []) = let (r:rs) = reverse ls+                       in CList [f] r rs++{- Manipulating Packing -}++-- |Balance the CList. Equivalent to `fromList . toList`+balance :: CList a -> CList a+balance = fromList . toList++-- |Move all elements to the left side of the CList.+packL :: CList a -> CList a+packL Empty = Empty+packL (CList l f r) = CList (l ++ (reverse r)) f []++-- |Move all elements to the right side of the CList.+packR :: CList a -> CList a+packR Empty = Empty+packR (CList l f r) = CList [] f (r ++ (reverse l))++{- Information -}++-- |Returns true if the CList is empty.+isEmpty :: CList a -> Bool+isEmpty Empty = True+isEmpty _ = False++-- |Return the size of the CList.+size :: CList a -> Int+size Empty = 0+size (CList l _ r) = 1 + (length l) + (length r)++{- Instances -}++-- | The show instance prints a tuple of the+-- balanced CList where the left list's right-most+-- element is the first element to the left. The+-- left most-most element of the right list is the+-- next element to the right.+instance (Show a) => Show (CList a) where+    show cl = case balance cl of+                     (CList l f r) -> show (reverse l,f,r)+                     Empty -> "Empty"++instance Arbitrary a => Arbitrary (CList a) where+    arbitrary = frequency [(1, return Empty), (10, arbCList)]+        where arbCList = do+                l <- arbitrary+                f <- arbitrary+                r <- arbitrary+                return $ CList l f r+    shrink (CList l f r) = Empty : [ CList l' f' r' | l' <- shrink l,+                                                    f' <- shrink f,+                                                    r' <- shrink r]+    shrink Empty = []++instance Functor CList where+    fmap _ Empty = Empty+    fmap fn (CList l f r) = (CList (fmap fn l) (fn f) (fmap fn r))