#4019: deriving Ord can produce incorrect and inefficient instances
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Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.14.1
Component: Compiler | Version: 6.13
Keywords: | Difficulty:
Os: Unknown/Multiple | Testcase:
Architecture: Unknown/Multiple | Failure: Incorrect result at runtime
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Comment(by simonpj):
Thank you very much for producing a patch. By a rare coincidence I spent
some time on Friday night doing the job myself! Moreover, I completely
re-engineered the general scheme for `Ord` comparisons, as you'll see when
you look at my patch, which should give a useful performance boost.
So, with apologies to you, I'll incorporate my patch, but with many thanks
for your work. Please don't be discouraged. This doesn't happen often.
There are quite a few tickets of a similar nature that we'd like help
with, such as
* #3676: realToFrac conversions
* #3744: comparisons against minBound and maxBound are not optimised
away
* #3065: quot is sub-optimal
* #2269: Word type to Double or Float conversions
* #2271: floor, ceiling, round :: Double -> Int are awesomely slow
* #1434: slow conversion Double to Int
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4019#comment:6>
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