do-let-function-binding-nested.hs

{- ORACLE_TEST pass -}
module ExprDoLetFunctionBindingNested where

memoIO f = do
    v <- newMVar M.empty
    let f' x = do
            m <- readMVar v
            case M.lookup x m of
                Nothing -> do let { r = f x }; modifyMVar_ v (return . M.insert x r); return r
                Just r  -> return r
    return f'