[GHC] #1960: Add Applicative and Monoid instances for STM

[GHC]

#1960: Add Applicative and Monoid instances for STM
-------------------------------+--------------------------------------------
    Reporter:  conal           |       Owner:         
        Type:  proposal        |      Status:  new    
    Priority:  normal          |   Milestone:         
   Component:  libraries/base  |     Version:  6.8.1  
    Severity:  normal          |    Keywords:         
  Difficulty:  Easy (1 hr)     |    Testcase:         
Architecture:  Unknown         |          Os:  Unknown
-------------------------------+--------------------------------------------
 {{{
 instance Applicative STM where { pure = return; (<*>) = ap }

 instance Monoid (STM a) where { mempty = retry; mappend = orElse }
 }}}

 I don't know where these instances would go.  Nor whether this is a
 libraries or GHC proposal.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1960>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler