[Haskell-cafe] ANNOUNCE: compose-trans-0.0

Miguel Mitrofanov miguelimo38 at yandex.ru
Mon Aug 17 01:06:24 EDT 2009

Just uploaded compose-trans-0.0 to Hackage.

'compose-trans' is a small library intended to make monad transformers  
composable. It provides a class TransM, derived from MonadTrans, which  
is closed under composition - that is, if t1 and t2 are instances of  
TransM, then (t2 :. t1) is also an instance of TransM (and, therefore,  
an instance of MonadTrans), and the type ((t2 :. t1) m x) is  
isomorphic to (t2 (t1 m) x). It's fairly easy to make a new  
transformer an instance of TransM; it only takes one short line of code.

There are also TransP and TransF classes, that help dealing with  
MonadPlus and MonadFix instances.

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