[GHC] #9398: Data.List.cycle is not a good producer

[GHC]

#9398: Data.List.cycle is not a good producer
-------------------------------------+-------------------------------------
              Reporter:  dfeuer      |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.8.4
             Component:              |          Version:  7.8.3
  libraries/base                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Easy (less than 1
  Unknown/Multiple                   |  hour)
       Type of failure:  Runtime     |       Blocked By:
  performance bug                    |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------

Comment (by dfeuer):

 Replying to [comment:7 nomeata]:
 > I think you meant
 >  {{{#!hs
 >  cycle [] = let cyc = augment cycle' cyc in cyc
 >    where
 >      cycle' c n = foldr c n []
 >
 >  cycle [] = let cyc = augment (\c n -> n) cyc in cyc

 I don't think so. Substituting `[]` for `xs`, `cycle' c n = foldr c n [] =
 []`, so `cycle' = \c n -> []`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9398#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler