The library allows to cache result of an asynchronous computation for no longer than a given period of time.
In order to use the package you should add the package to the dependency section of the cabal file of your package.
In order to use the cache you should create a 'Handle'
{-# LANGUAGE ImportQualifiedPost #-}
{-# LANGUAGE NumericUnderscores #-}
{-# LANGUAGE BlockArguments #-}
import Control.Concurrent
import System.Cache qualified as Cache
import System.Cache.Impl.Ghc qualified as Cache.Ghc
import System.Clock.Seconds
main :: IO ()
main = do
cache <- Cache.Ghc.new do
Cache.mkConfig 60 Monotonic
-- we create a cached version of computation
-- in order to hide implementation
let cachedTimeout input = Cache.requestOr cache input \i -> do
threadDelay $ i * 1_000_000
pure i
-- We use our cached function
print (cachedTimeout 1)
print (cachedTimeout 1)
print (cachedTimeout 2)sh-3.2$ runhaskell local.hs | ts -S
00:00:03 2
00:00:03 2
00:00:06 3
When running the program first we wait for 2 seconds, the next call returns immediately. The third one is long as it uses a new input value.
cabal configure
cabal build
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