[GHC] #8920: Alternative GADT syntax

22 Mar 2014


      #8920: Alternative GADT syntax
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       Reporter:  guest                       |             Owner:
           Type:  feature request             |            Status:  new
       Priority:  normal                      |         Milestone:  7.10.1
      Component:  Compiler (Parser)           |           Version:
       Keywords:  gadts                       |  7.8.1-rc2
   Architecture:  Unknown/Multiple            |  Operating System:
     Difficulty:  Moderate (less than a day)  |  Unknown/Multiple
     Blocked By:                              |   Type of failure:  Other
Related Tickets:                              |         Test Case:
                                              |          Blocking:
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 An alternative syntax for GADTs

 Instead of
 {{{
 data Term x where
     K :: Term (a -> b -> a)
     S :: Term ((a -> b -> c)  -> (a -> b) -> a -> c)
     Const :: a -> Term a
     (:@) :: Term (a -> b) -> (Term a) -> Term b
 }}}

 You can write
 {{{
 data Term x = K :: Term (a -> b -> a) | S :: Term ((a -> b -> c)  -> (a ->
 b) -> a -> c) | Const a :: Term a | (:@) (Term (a -> b)) (Term a) :: Term
 b
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8920
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