cached-io (empty) → 0.1.0.1
raw patch · 5 files changed
+319/−0 lines, 5 filesdep +basedep +stmdep +timesetup-changed
Dependencies added: base, stm, time
Files
- LICENSE +202/−0
- Setup.hs +2/−0
- cached-io.cabal +61/−0
- src/Control/Concurrent/CachedIO.hs +33/−0
- test/test-cachedIO.hs +21/−0
+ LICENSE view
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+ Setup.hs view
@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain
+ cached-io.cabal view
@@ -0,0 +1,61 @@+-- Initial cached-io.cabal generated by cabal init. For further+-- documentation, see http://haskell.org/cabal/users-guide/++name: cached-io+version: 0.1.0.1+synopsis:+ A simple library to cache a single IO action with timeout+description:+ A simple library that caches an expensive IO action. This produces an IO+ action that, when run, either runs the expensive action and saves its result+ for a period of time, or re-uses the saved value. This amortizes the cost of+ the expensive IO action without a lot of complexity.++ See the test program for an example of how to use it.+license: Apache-2.0+license-file: LICENSE+author: SumAll, Inc.+maintainer: eglassercamp@sumall.com+-- copyright:+category: Development+build-type: Simple+-- extra-source-files:+cabal-version: >=1.10++source-repository head+ type: tag+ location: git://github.com:SumAll/haskell-cached-io.git++library+ exposed-modules: Control.Concurrent.CachedIO+ -- other-modules:+ -- other-extensions:+ build-depends:+ base >=4.7 && <4.8,+ stm,+ time+ hs-source-dirs: src/+ default-language: Haskell2010+ ghc-options: -rtsopts -fwarn-unused-imports -Wall+ -fno-warn-unused-do-bind+ if flag(developer)+ ghc-options: -Werror++flag developer+ manual: True+ default: False+ description:+ compile with -Werror to make warnings fatal++executable test-cachedIO+ main-is: test-cachedIO.hs+ build-depends:+ base >=4.7 && <4.8,+ stm,+ time+ hs-source-dirs: src/, test/+ default-language: Haskell2010+ ghc-options: -threaded -rtsopts -fwarn-unused-imports -Wall+ -fno-warn-unused-do-bind+ if flag(developer)+ ghc-options: -Werror
+ src/Control/Concurrent/CachedIO.hs view
@@ -0,0 +1,33 @@+module Control.Concurrent.CachedIO (+ cachedIO+ ) where++import Control.Concurrent.STM (atomically, newTVar, readTVar, writeTVar)+import Control.Monad (join)+import Data.Time.Clock (NominalDiffTime, addUTCTime, getCurrentTime)++-- | Cache an IO action, producing a version of this IO action that is cached+-- for 'interval' seconds. Immediately initialize the cache with the given IO+-- action.+--+-- The outer IO is responsible for setting up the cache. Use the inner one to+-- either get the cached value or refresh, if the cache is older than 'interval'+-- seconds.+cachedIO :: NominalDiffTime -> IO a -> IO (IO a)+cachedIO interval io = do+ initValue <- io+ initTime <- getCurrentTime+ cachedT <- atomically (newTVar (initTime, initValue))+ return $ do+ now <- getCurrentTime+ join . atomically $ do+ cached <- readTVar cachedT+ case cached of+ (lastUpdated, value) | addUTCTime interval lastUpdated > now ->+ return (return value)+ (_, value) -> do+ writeTVar cachedT (now, value)+ return $ do+ newValue <- io+ atomically (writeTVar cachedT (now, newValue))+ return newValue
+ test/test-cachedIO.hs view
@@ -0,0 +1,21 @@+import Control.Concurrent.CachedIO (cachedIO)+import Data.List (isInfixOf)++crawlTheInternet :: IO [String]+crawlTheInternet = do+ putStrLn "Scanning pages.."+ putStrLn "Parsing HTML.."+ putStrLn "Following links.."+ return ["website about Haskell", "website about Ruby", "slashdot.org",+ "The Monad.Reader", "haskellwiki"]++searchEngine :: String -> IO [String] -> IO [String]+searchEngine query internet = do+ pages <- internet+ return $ filter (query `isInfixOf`) pages++main :: IO ()+main = do+ cachedInternet <- cachedIO 600 crawlTheInternet -- 10 minute cache+ print =<< searchEngine "Haskell" cachedInternet+ print =<< searchEngine "C#" cachedInternet