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Gmane
From: Miguel Mitrofanov <miguelimo38 <at> yandex.ru>
Subject: ANNOUNCE: compose-trans-0.0
Newsgroups: gmane.comp.lang.haskell.cafe
Date: Monday 17th August 2009 05:06:24 UTC (over 8 years ago)
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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