[GHC] #11740: RFC kind synonyms

[GHC]

#11740: RFC kind synonyms
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:  wontfix           |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Iceland_jack):

 {{{#!hs
 type Monadish    = Type -> Type
 type Transformer = Monadish -> Monadish
 }}}

 with many examples from Edward's work on
 [https://www.reddit.com/r/haskell/comments/50rxci/edward_kmett_monad_homomorphisms_google_tech_talk/d76tmnm
 monad morphisms]

 {{{#!hs
 newtype Tensor :: Transformer -> Transformer -> Transformer where
   Tensor :: s (t m) a -> Tensor s t m a

 class MonadTrans (t :: Transformer)

 class Commute (s :: Transformer) (t :: Transformer) where
   commute :: Monad m => s (t m) a -> t (s m) a

 newtype StateT s :: Transformer where
   StateT :: (s -> m (a, s)) -> StateT s m a

 newtype WriterT w :: Transformer where
   WriterT :: m (a, w) -> WriterT w m a
 }}}

 etc.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11740#comment:8>
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