On Thu, 2009-12-31 at 04:59 -0500, John Van Enk wrote:
> Hi List,
>
> I recently needed a ring structure (circular list with bi-directional
> access) and didn't see anything obvious on Hackage. I threw something
> together fairly quickly and would like some feedback before tossing it
> on Hackage.
>
> I'd really appreciate if some one would:
> 1. make sure the code looks goodish (127 lines with full docs)
> 2. make sure my tests look saneish
> If I hear nothing, I'll assume wild support and push to Hackage.
>
> Code: http://github.com/sw17ch/data-ring/blob/master/src/Data/Ring.hs
> Tests:
> http://github.com/sw17ch/data-ring/blob/master/tests/quickcheck.hs
> Package Root: http://github.com/sw17ch/data-ring
>
> Thanks ahead of time,
> John Van Enk
Monad, MonadPlus, Applicative, Alternative, Foldable and Traversable.
About comonad - not exactly as every comonad is copointed and the only
possible way is extract Empty = _|_
Regards
From 5f8bb8eeaabe6d2b82cd68ba99272603b82d9c67 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:00:33 +0100
Subject: [PATCH 1/6] Added Monad instance
---
src/Data/CircularList.hs | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index 24e5bb9..17b7bba 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -230,3 +230,7 @@ instance Arbitrary a => Arbitrary (CList a) where
instance Functor CList where
fmap _ Empty = Empty
fmap fn (CList l f r) = (CList (fmap fn l) (fn f) (fmap fn r))
+
+instance Monad CList where
+ return = singleton
+ m >>= f = fromList $ concat $ toList $ fmap (toList . f) m
--
1.6.6
From a0841065478225c7d7beff39fc206ed6b4be35e8 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:01:33 +0100
Subject: [PATCH 2/6] Added MonadPlus instance
---
src/Data/CircularList.hs | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index 17b7bba..cfd39b6 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -66,6 +66,7 @@ module Data.CircularList (
isEmpty, size,
) where
+import Control.Monad
import Test.QuickCheck.Arbitrary
import Test.QuickCheck.Gen
@@ -234,3 +235,8 @@ instance Functor CList where
instance Monad CList where
return = singleton
m >>= f = fromList $ concat $ toList $ fmap (toList . f) m
+
+instance MonadPlus CList where
+ mzero = Empty
+ (CList l v r) `mplus` c = (CList l v (r++toList c))
+ Empty `mplus` c = c
\ No newline at end of file
--
1.6.6
From 7ad6834537d63ba511ff37b2a490d89bde8a4a02 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:02:34 +0100
Subject: [PATCH 3/6] Added Applicative instance
---
src/Data/CircularList.hs | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index cfd39b6..09defe3 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -66,6 +66,7 @@ module Data.CircularList (
isEmpty, size,
) where
+import Control.Applicative hiding (empty)
import Control.Monad
import Test.QuickCheck.Arbitrary
import Test.QuickCheck.Gen
@@ -232,6 +233,10 @@ instance Functor CList where
fmap _ Empty = Empty
fmap fn (CList l f r) = (CList (fmap fn l) (fn f) (fmap fn r))
+instance Applicative CList where
+ pure = return
+ (<*>) = ap
+
instance Monad CList where
return = singleton
m >>= f = fromList $ concat $ toList $ fmap (toList . f) m
--
1.6.6
From 8a49a4658ad5fc6da96cb688e4a8761415ac2678 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:03:38 +0100
Subject: [PATCH 4/6] Added Alternative instance
---
src/Data/CircularList.hs | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index 09defe3..ffbc735 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -67,6 +67,7 @@ module Data.CircularList (
) where
import Control.Applicative hiding (empty)
+import qualified Control.Applicative
import Control.Monad
import Test.QuickCheck.Arbitrary
import Test.QuickCheck.Gen
@@ -237,6 +238,10 @@ instance Applicative CList where
pure = return
(<*>) = ap
+instance Alternative CList where
+ empty = mzero
+ (<|>) = mplus
+
instance Monad CList where
return = singleton
m >>= f = fromList $ concat $ toList $ fmap (toList . f) m
--
1.6.6
From c930f1f86a676620df317ef0e3a90d52b527ca59 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:19:01 +0100
Subject: [PATCH 5/6] Added Foldable instance
---
src/Data/CircularList.hs | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index ffbc735..d976a40 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -69,6 +69,8 @@ module Data.CircularList (
import Control.Applicative hiding (empty)
import qualified Control.Applicative
import Control.Monad
+import Data.Foldable (Foldable)
+import qualified Data.Foldable
import Test.QuickCheck.Arbitrary
import Test.QuickCheck.Gen
@@ -249,4 +251,8 @@ instance Monad CList where
instance MonadPlus CList where
mzero = Empty
(CList l v r) `mplus` c = (CList l v (r++toList c))
- Empty `mplus` c = c
\ No newline at end of file
+ Empty `mplus` c = c
+
+instance Foldable CList where
+ foldr f i = foldr f i . toList
+ foldl f i = foldl f i . toList
--
1.6.6
From 7d92a2a4210fb1b221dcab599c567ae5c3511457 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:26:38 +0100
Subject: [PATCH 6/6] Added Traversable instance
---
src/Data/CircularList.hs | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index d976a40..6e8065e 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -71,6 +71,8 @@ import qualified Control.Applicative
import Control.Monad
import Data.Foldable (Foldable)
import qualified Data.Foldable
+import Data.Traversable hiding (mapM)
+import qualified Data.Traversable
import Test.QuickCheck.Arbitrary
import Test.QuickCheck.Gen
@@ -256,3 +258,7 @@ instance MonadPlus CList where
instance Foldable CList where
foldr f i = foldr f i . toList
foldl f i = foldl f i . toList
+
+instance Traversable CList where
+ traverse f = fmap fromList . traverse f . toList
+ mapM f = liftM fromList . mapM f . toList
--
1.6.6
From 80f98d06861b878caf306699f1651597b4adaa60 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:35:00 +0100
Subject: [PATCH 7/9] Added Pointed instance
---
src/Data/CircularList.hs | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index 6e8065e..690fd6e 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -68,6 +68,7 @@ module Data.CircularList (
import Control.Applicative hiding (empty)
import qualified Control.Applicative
+import Control.Comonad
import Control.Monad
import Data.Foldable (Foldable)
import qualified Data.Foldable
@@ -238,6 +239,9 @@ instance Functor CList where
fmap _ Empty = Empty
fmap fn (CList l f r) = (CList (fmap fn l) (fn f) (fmap fn r))
+instance Pointed CList where
+ point = return
+
instance Applicative CList where
pure = return
(<*>) = ap
@@ -262,3 +266,4 @@ instance Foldable CList where
instance Traversable CList where
traverse f = fmap fromList . traverse f . toList
mapM f = liftM fromList . mapM f . toList
+
--
1.6.6
From dfaa055d5d6c8b1b54fd09288fdd4815179b7852 Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:36:15 +0100
Subject: [PATCH 8/9] Added Copointed instance
---
src/Data/CircularList.hs | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index 690fd6e..74dc83c 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -259,6 +259,10 @@ instance MonadPlus CList where
(CList l v r) `mplus` c = (CList l v (r++toList c))
Empty `mplus` c = c
+instance Copointed CList where
+ extract Empty = error "Extracting from empty ring"
+ extract (CList _ v _) = v
+
instance Foldable CList where
foldr f i = foldr f i . toList
foldl f i = foldl f i . toList
--
1.6.6
From 907304d1cd5bf14e1dfe26fc302955a4c238f93a Mon Sep 17 00:00:00 2001
From: Maciej Piechotka <uzytkown...@gmail.com>
Date: Mon, 4 Jan 2010 14:47:37 +0100
Subject: [PATCH 9/9] Added Comonad instance
---
src/Data/CircularList.hs | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/src/Data/CircularList.hs b/src/Data/CircularList.hs
index 74dc83c..ad0ae1a 100644
--- a/src/Data/CircularList.hs
+++ b/src/Data/CircularList.hs
@@ -263,6 +263,17 @@ instance Copointed CList where
extract Empty = error "Extracting from empty ring"
extract (CList _ v _) = v
+instance Comonad CList where
+ duplicate c = CList (dupLeft c) c (dupRight c)
+ where dupRight Empty = []
+ dupRight (CList _ _ []) = []
+ dupRight (CList l v (r:rs)) = let next = CList (v:l) r rs
+ in next:dupRight next
+ dupLeft Empty = []
+ dupLeft (CList [] _ _) = []
+ dupLeft (CList (l:ls) v r) = let prev = CList (v:r) l ls
+ in prev:dupLeft prev
+
instance Foldable CList where
foldr f i = foldr f i . toList
foldl f i = foldl f i . toList
--
1.6.6
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