[GHC] #4887: add a Location interface for element-wise operations on Data.Map

[GHC]

#4887: add a Location interface for element-wise operations on Data.Map
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    Reporter:  ross              |       Owner:                   
        Type:  proposal          |      Status:  new              
    Priority:  normal            |   Component:  libraries (other)
     Version:  7.0.1             |    Keywords:                   
    Testcase:                    |   Blockedby:                   
          Os:  Unknown/Multiple  |    Blocking:                   
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown     
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 This is a variant of a suggestion by apfelmus:

   http://www.haskell.org/pipermail/libraries/2010-September/014510.html

 To avoid proliferation of variants of element-wise operations, the idea is
 to split these operations into two phases mediated by a new Location type,
 so that users can do whatever they like between these phases.
 Documentation is here:

   http://code.haskell.org/~ross/containers_doc/Data-Map.html#3

 This adds a type and 9 functions to the interface, but makes possible
 monadic updates and much more.  As an illustration, the file
 {{{MapOps.hs}}} attached to the ticket gives definitions of 30 of the
 public functions of Data.Map in terms of the new interface.  At least in
 the case of insert, this definition is slightly faster than the current
 one.

 Discussion period: 4 weeks (to 4 February)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4887>
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