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