Practical principled FRP: Forget the past, change the future, FRPNow!

We present a new interface for practical Functional Reactive Programming (FRP) that (1) is close in spirit to the original FRP ideas, (2) does not have the original space-leak problems, without using arrows or advanced types, and (3) provides a simple and expressive way for performing IO actions from FRP code. We also provide a denotational semantics for this new interface, and a technique (using Kripke logical relations) for reasoning about which FRP functions may "forget their past", i.e. which functions do not have an inherent space-leak. Finally, we show how we have implemented this interface as a Haskell library called FRPNow

The Key monad: Type-safe unconstrained dynamic typing

We present a small extension to Haskell called the Key monad. With the Key monad, unique keys of different types can be created and can be tested for equality. When two keys are equal, we also obtain a concrete proof that their types are equal. This gives us a form of dynamic typing, without the need for Typeable constraints. We show that our extension allows us to safely do things we could not otherwise do: it allows us to implement the ST monad (inefficiently), to implement an embedded form of arrow notation, and to translate parametric HOAS to typed de Bruijn indices, among others. Although strongly related to the ST monad, the Key monad is simpler and might be easier to prove safe. We do not provide such a proof of the safety of the Key monad, but we note that, surprisingly, a full proof of the safety of the ST monad also remains elusive to this day. Hence, another reason for studying the Key monad is that a safety proof for it might be a stepping stone towards a safety proof of the ST monad

Decompensation as initial presentation in patients with liver cirrhosis is associated with an increased risk of future decompensation and mortality

Background and Aims: The clinical course of patients with liver cirrhosis and adherence to hepatocellular carcinoma (HCC) screening guidelines are not well studied in the Netherlands. We investigated this and potential risk factors for decompensation and transplant-free survival (TFS) in a large regional cohort. Methods: We performed a retrospective cohort study of patients with confirmed liver cirrhosis in Amsterdam, the Netherlands. Clinical parameters, decompensation events, development of HCC, and medication use were extracted from medical records. Results: In total, 681 hospitalized and outpatients were included. Mortality risk was increased by: age (aHR 1.07, p < 0.01), smoking (aHR 1.83, p < 0.01), decompensated initial presentation (aHR 1.43, p = 0.04) and increased MELD (aHR 1.07, p < 0.01). PPI use tended to increase mortality risk (aHR 1.35, p = 0.05). The risk of future decompensation was increased with increased age (aHR 1.02, p < 0.01), decompensated initial presentation (aHR 1.37, p = 0.03) and alcohol misuse as etiology (aHR 1.34, p = 0.04). Adequately screened patients for HCC had a longer TFS compared to patients who were not (48 vs 22 months), p < 0.01). Conclusions: In patients with cirrhosis, decompensation at initial presentation was associated with an increased risk of future decompensation and mortality. Alcoholic cirrhosis was associated with an increased risk of future decompensation. Adequate HCC surveillance was associated with markedly better survival