[Hackage] #369: Version ranges should be simplified before printing

[Hackage]

#369: Version ranges should be simplified before printing
----------------------------+-----------------------------------------------
  Reporter:  nominolo       |        Owner:                     
      Type:  defect         |       Status:  new                
  Priority:  normal         |    Milestone:  Cabal-1.8          
 Component:  Cabal library  |      Version:  HEAD               
  Severity:  minor          |   Resolution:                     
  Keywords:                 |   Difficulty:  very easy (<1 hour)
Ghcversion:                 |     Platform:                     
----------------------------+-----------------------------------------------
Changes (by duncan):

  * difficulty:  normal => very easy (<1 hour)
  * ghcversion:  6.9 =>
  * milestone:  => Cabal-1.8

Comment:

 Sometimes these are quite entertainingly long. For example with happstack-
 server:

 {{{
 cabal: Unresolved dependencies: base >=3&&<4, base >=3&&<4,
 base >=3&&<4, base >=3&&<4, base >=3&&<4, base >=3&&<4,
 base >=3&&<4, base >=3&&<4, base >=3&&<4
 }}}

 No, really. :-)

 With the new version intervals adt we've got a function:
 {{{
 simplifyVersionRange :: VersionRange -> VersionRange
 }}}
 which should make this stuff easy. Just take the intersection of version
 constraints per-package and simplify and print. A slightly more
 sophisticated approach would be to check that taking intersections does
 not end up with an empty range, ie that the constraints are necessarily
 unsatisfiable irrespective of potential available packages. The intervals
 adt also makes this check easy and efficient.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/369#comment:3>
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