[GHC] #393: functions without implementations

[GHC]

#393: functions without implementations
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        Reporter:  c_maeder          |                Owner:  Iceland_jack
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  ⊥
       Component:  Compiler (Type    |              Version:  None
  checker)                           |
      Resolution:                    |             Keywords:  newcomer
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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Changes (by Iceland_jack):

 * owner:   => Iceland_jack


Comment:

 Code from discussion thread [https://github.com/ramda/ramda-
 lens/pull/2#issuecomment-181955004 comment] would be valid:

 > The only way to write such a function is to use methods in the
 `Profunctor` interface of which there is only 1. Thus, if we have any
 value `i :: Iso s a` we know it must be of the form
 >
 > {{{#!hs
 > i = dimap fwd bck
 >   where
 >     fwd :: s -> a
 >     bck :: a -> s
 > }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/393#comment:36>
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