refcount (empty) → 0.0.0

raw patch · 3 files changed

+65/−0 lines, 3 filesdep +basedep +hashabledep +unordered-containerssetup-changed

Dependencies added: base, hashable, unordered-containers

Files

• Data/Refcount.hs +39/−0
• Setup.hs +2/−0
• refcount.cabal +24/−0

@@ -0,0 +1,39 @@+module Data.Refcount ( Refcount (..)+                     , refcounted+                     , insertRef+                     , deleteRef+                     , removeRef+                     ) where++import Control.Applicative ((<$>))+import Data.Monoid+import Data.Hashable+import Data.HashMap.Strict as HashMap++-- | Maintain a collection of objects with duplication counts.+newtype Refcount a = Refcount { unRefcount :: HashMap a Int }++instance (Hashable a, Eq a) => Monoid (Refcount a) where+  mempty = Refcount empty+  mappend (Refcount a) (Refcount b) = Refcount $ unionWith (+) a b++-- | Retrieve the refcounted objects.+refcounted :: Refcount a -> [a]+refcounted = keys . unRefcount++-- | Insert an object and increment its count.+insertRef :: (Hashable a, Eq a) => a -> Refcount a -> Refcount a+insertRef a (Refcount m) = Refcount $ insertWith (+) a 1 m++-- | Remove a reference to an element and decrease its count, possibly removing it from the set.+-- Returns @Nothing@ if the element wasn't found, or @Just set@.+deleteRef :: (Hashable a, Eq a) => a -> Refcount a -> Maybe (Refcount a)+deleteRef a r = snd <$> removeRef a r++-- | Remove a reference to an element and decrease its count, possibly removing it from the set.+-- Returns @Nothing@ if the element wasn't found, or @Just (wasRemoved, set)@.+removeRef :: (Hashable a, Eq a) => a -> Refcount a -> Maybe (Bool, Refcount a)+removeRef a (Refcount m) = fmap decRef $ HashMap.lookup a m+  where decRef count = if count > 1+                       then (False, Refcount $ adjust (subtract 1) a m)+                       else (True, Refcount $ delete a m)

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,24 @@+name:               refcount+version:            0.0.0+synopsis:           Container with element counts+category:           Data+license:            MIT+author:             Ben Foppa+stability:          Experimental+homepage:           https://github.com/RobotGymnast/refcount+maintainer:         benjamin.foppa@gmail.com+build-type:         Simple+cabal-version:      >= 1.9.2++library+    hs-source-dirs:   .+    ghc-options:      -Wall -threaded -rtsopts=all+    exposed-modules:  Data.Refcount++    build-depends: base == 4.*+                 , hashable == 1.2.1.*+                 , unordered-containers == 0.2.4.*++source-repository head+  type: git+  location: https://github.com/RobotGymnast/refcount