#4019: deriving Ord can produce incorrect and inefficient instances -------------------------------------+------------------------------------- Reporter: rl | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 6.13 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Incorrect | Blocked By: result at runtime | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by thomie): * difficulty: => Unknown * milestone: 7.10.1 => Comment: This was fixed in 2010. A regression test is missing. commit f3c7ab8dbd5a46ef5a7aeeb398a6d4bc1482e606 {{{ Author: Simon Peyton Jones <> Date: Mon May 10 13:33:33 2010 +0000 Re-engineer the derived Ord instance generation code (fix Trac #4019) As well as fixing #4019, I rejigged the way that Ord instances are generated, which should make them faster in general. See the Note [Generating Ord instances]. I tried to measure the performance difference from this change, but the #4019 fix only removes one conditional branch per iteration, and I couldn't measure a consistent improvement. But still, tihs is better than before. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/4019#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler