Sha256: ffa87763259c1e653327222bf23d29c662e68294d3d94c550e4d87b80cd93e64
Contents?: true
Size: 735 Bytes
Versions: 328
Compression:
Stored size: 735 Bytes
Contents
module BankAccount ( BankAccount
, openAccount, closeAccount
, getBalance, incrementBalance) where
import Control.Concurrent.STM
newtype BankAccount = BankAccount { unBankAccount :: TVar (Maybe Int) }
openAccount :: IO BankAccount
openAccount = atomically $ BankAccount <$> newTVar (Just 0)
closeAccount :: BankAccount -> IO ()
closeAccount = atomically . flip writeTVar Nothing . unBankAccount
getBalance :: BankAccount -> IO (Maybe Int)
getBalance = atomically . readTVar . unBankAccount
incrementBalance :: BankAccount -> Int -> IO (Maybe Int)
incrementBalance acct delta = atomically $ do
let b = unBankAccount acct
bal <- fmap (delta +) <$> readTVar b
writeTVar b bal
return bal
Version data entries
328 entries across 328 versions & 1 rubygems