[GHC] #7828: RebindableSyntax and Arrow

[GHC]

#7828: RebindableSyntax and Arrow
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        Reporter:  AlessandroVermeulen        |            Owner:
            Type:  bug                        |  jstolarek
        Priority:  normal                     |           Status:  new
       Component:  Compiler (Type checker)    |        Milestone:  7.10.1
      Resolution:                             |          Version:  7.6.2
Operating System:  Unknown/Multiple           |         Keywords:
 Type of failure:  GHC rejects valid program  |     Architecture:
       Test Case:                             |  Unknown/Multiple
        Blocking:                             |       Difficulty:  Unknown
                                              |       Blocked By:
                                              |  Related Tickets:  #1537,
                                              |  #3613
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Comment (by ross):

 Replying to [comment:37 jstolarek]:
 > Now I see this was even mentioned in "A New Notation for Arrows" paper.
 Again there's something I don't understand here. So far I though that
 stack is an implicit mechanism that is used to pass around values bound
 using `<-`. But here it seems that the user is allowed to explicitly
 access the stack. Isn't that a bit risky?
 The local environment is used to pass around values bound inside the
 `proc` expression.  The stack is used to pass around anonymous values.
 They can be pushed using application, popped and named in the environment
 by command lambda, and also manipulated by control operators.  The type
 constraints on operators keep them well behaved.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7828#comment:38>
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