[ ghc-Bugs-643878 ] sortBy not stable

Bugs item #643878, was opened at 2002-11-26 01:12
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=643878&group_id=8032

Category: Prelude
Group: 5.04.1
>Status: Closed
>Resolution: Fixed
Priority: 7
Submitted By: Mike Gunter (magunter)
Assigned to: Nobody/Anonymous (nobody)
Summary: sortBy not stable

Initial Comment:
The library report requires that sortBy be stable.  In
5.04.1 it isn't:

  gunter.philco.com[1995]$ ghci
     ___         ___ _
    / _ \ /\  /\/ __(_)
   / /_\// /_/ / /  | |      GHC Interactive, version
5.04, for Haskell 98.
  / /_\/ __  / /___| |      http://www.haskell.org/ghc/
  \____/\/ /_/\____/|_|      Type :? for help.
  
  Loading package base ... linking ... done.
  Loading package haskell98 ... linking ... done.
  Prelude> List.sortBy (\ (_,a) (_,b) -> compare a b) $
zip [0..] [100,0,0,0]
  [(3,0),(2,0),(1,0),(0,100)]

.  In 5.02.3, it was stable:

  c966553-A[2314]$ ghci
     ___         ___ _
    / _ \ /\  /\/ __(_)
   / /_\// /_/ / /  | |      GHC Interactive, version
5.02.3, for Haskell 98.
  / /_\/ __  / /___| |      http://www.haskell.org/ghc/
  \____/\/ /_/\____/|_|      Type :? for help.
  
  Loading package std ... linking ... done.
  Prelude> List.sortBy (\ (_,a) (_,b) -> compare a b) $
zip [0..] [100,0,0,0]
  [(1,0),(2,0),(3,0),(0,100)]


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>Comment By: Simon Marlow (simonmar)
Date: 2002-11-26 09:52

Message:
Logged In: YES 
user_id=48280

This one has been fixed, grab 5.04.2 when it is released.

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