Comments on: Are continuations really the mother of all monads? http://blog.melding-monads.com/2009/12/20/are-continuations-really-the-mother-of-all-monads/ Math, Computer Science, and Education Thu, 22 Jul 2010 12:20:42 +0000 hourly 1 http://wordpress.com/ By: lpsmith http://blog.melding-monads.com/2009/12/20/are-continuations-really-the-mother-of-all-monads/#comment-65 lpsmith Sat, 06 Feb 2010 21:47:20 +0000 http://blog.melding-monads.com/?p=132#comment-65 It was pointed out to me by Russell O'Connor, Dan Doel, and others that <code>StateT st (Cont r)</code> is in fact the exact same monad as <code>ContT r (State st)</code> in the context of the Monad Transformer Library. However, <a href="http://www.fceia.unr.edu.ar/~mauro/" rel="nofollow">Mauro Jaskelioff</a> in his paper <a href="http://www.fceia.unr.edu.ar/~mauro/pubs/mmt/mmt.pdf" rel="nofollow">Modular Monad Transformers</a> argues in Section 4 that it is more natural for <code>callCC</code> to be lifted differently in the <code>StateT st (Cont r)</code> case, so that it differs from the instance of <code>callCC</code> for <code>ContT r (State st)</code>. According to Jaskelioff, the MTL's lifting is correct in the second case, but not in the first. The two liftings are also mentioned in Monad Transformers and Modular Interpreters in Section 8.3, which includes a few other references to where each has appeared in the literature. It was pointed out to me by Russell O’Connor, Dan Doel, and others that StateT st (Cont r) is in fact the exact same monad as ContT r (State st) in the context of the Monad Transformer Library. However, Mauro Jaskelioff in his paper Modular Monad Transformers argues in Section 4 that it is more natural for callCC to be lifted differently in the StateT st (Cont r) case, so that it differs from the instance of callCC for ContT r (State st). According to Jaskelioff, the MTL’s lifting is correct in the second case, but not in the first.

The two liftings are also mentioned in Monad Transformers and Modular Interpreters in Section 8.3, which includes a few other references to where each has appeared in the literature.

]]> By: Noam Zeilberger http://blog.melding-monads.com/2009/12/20/are-continuations-really-the-mother-of-all-monads/#comment-46 Noam Zeilberger Tue, 22 Dec 2009 20:22:39 +0000 http://blog.melding-monads.com/?p=132#comment-46 > One thing is clear, however: its tricky to generalize Filinski’s Representing Monads to lazy evaluation, if indeed it is possible to do so fully. You should read <a href="http://www.osl.iu.edu/publications/prints/2009/garcia09popl-lazy.pdf" rel="nofollow">Lazy Evaluation and Delimited Control</a> by Garcia, Lumsdaine and Sabry. I don't fully understand the paper yet, but I think it gives some sort of affirmative answer. > One thing is clear, however: its tricky to generalize Filinski’s Representing Monads to lazy evaluation, if indeed it is possible to do so fully.

You should read Lazy Evaluation and Delimited Control by Garcia, Lumsdaine and Sabry. I don’t fully understand the paper yet, but I think it gives some sort of affirmative answer.

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