#7436: Derived Foldable and Traversable instances become extremely inefficient 
to eta-expansion
  Reporter:  shachaf                  |          Owner:                  
      Type:  bug                      |         Status:  closed          
  Priority:  normal                   |      Milestone:                  
 Component:  Compiler                 |        Version:  7.6.1           
Resolution:  fixed                    |       Keywords:                  
        Os:  Unknown/Multiple         |   Architecture:  Unknown/Multiple
   Failure:  Runtime performance bug  |     Difficulty:  Unknown         
  Testcase:  perf/should_runt/T7436   |      Blockedby:                  
  Blocking:                           |        Related:                  
Changes (by simonpj):

  * status:  patch => closed
  * testcase:  => perf/should_runt/T7436
  * resolution:  => fixed


 commit 3d51f271e6819c52508956f2426c4c19dec0b2fb
 Author: Twan van Laarhoven <twa...@gmail.com>
 Date:   Thu Jan 3 16:24:42 2013 +0100

     Added note explaining the lambdas generated by functor deriving code,
 and how it compares to the old deriving code which used eta expansion.
 Thanks for the patches!

 I added a test in `perf/should_run`.  Interestingly the massive difference
 is run-time, not in allocation or residency.


Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7436#comment:17>
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