[GHC] #5162: Add Int index functions to Data.Set

[GHC]

#5162: Add Int index functions to Data.Set
---------------------------------+------------------------------------------
    Reporter:  sacundim          |       Owner:                   
        Type:  feature request   |      Status:  new              
    Priority:  normal            |   Component:  libraries (other)
     Version:  7.0.3             |    Keywords:  Data.Set         
    Testcase:                    |   Blockedby:                   
          Os:  Unknown/Multiple  |    Blocking:                   
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown     
---------------------------------+------------------------------------------
 Data.Map has some functions that allow a Map's entries to be accessed
 through Int indexes:

 {{{
 lookupIndex :: Ord k => k -> Map k a -> Maybe Int
 findIndex :: Ord k => k -> Map k a -> Int
 elemAt :: Int -> Map k a -> (k, a)
 updateAt :: (k -> a -> Maybe a) -> Int -> Map k a -> Map k a
 deleteAt :: Int -> Map k a -> Map k a
 }}}

 With the exception of updateAt, these functions are trivially adaptable to
 Data.Set.

 I attach a patch to this ticket that does that.  My Data.Set
 implementations of the functions are modeled on the ones from Data.Map.
 Functions implemented:

 {{{
 lookupIndex :: Ord a => a -> Set a -> Maybe Int
 findIndex :: Ord a => a -> Set a -> Int
 elemAt :: Int -> Set a -> a
 deleteAt :: Int -> Set a -> Set a
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5162>
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