Haskell by Example: Closures

original

import Data.IORef

intSeq :: IORef Int -> IO Int
intSeq ref = do
    modifyIORef ref (+1)
    readIORef ref

main = do
    ref <- newIORef 0
    let nextInt = intSeq ref

    print =<< nextInt
    print =<< nextInt
    print =<< nextInt

    ref' <- newIORef 0
    let newInts = intSeq ref'
    print =<< newInts

$ runhaskell closures.hs
1
2
3
1

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