Re: [GHC] #2076: rational infinities don't compare correctly to each other
#2076: rational infinities don't compare correctly to each other ---+ Reporter: uhollerbach | Owner: jeffrey Type: bug | Status: closed Priority: normal| Milestone: _|_ Component: libraries/base|Version: 6.8.2 Resolution: wontfix | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Difficulty: Unknown Testcase:| Blockedby: Blocking:|Related: ---+ Changes (by simonmar): * status: new = closed * resolution: = wontfix Comment: Lots of good discussion on this subject in #3676. I think we concluded that `Rational` does not include infinity as a value. Based on that, and the fact that `1%0` is actually `_|_`, I'm closing this ticket. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2076#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2076: rational infinities don't compare correctly to each other
#2076: rational infinities don't compare correctly to each other
-+--
Reporter: uhollerbach | Owner: jeffrey
Type: bug | Status: new
Priority: normal| Milestone: _|_
Component: libraries/base| Version: 6.8.2
Keywords:| Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown |Testcase:
Blockedby:|Blocking:
Related:|
-+--
Comment(by jeffrey):
In libraries/base/GHC/Real.lhs, I added
instance (Integral a) = Ord (Ratio a) where
{-# SPECIALIZE instance Ord Rational #-}
+ (x:%0) = (x':%0 ) = x0 || 0 x'
+ (x:%0) = (_ :%_ ) = x0
+ (_:%_) = (x':%0 ) = 0x'
(x:%y) = (x':%y') = x * y' = x' * y
+ (x:%0) (x':%0 ) = x0 0 x'
+ (x:%0) (_ :%_ ) = x0
+ (_:%_) (x':%0 ) = 0x'
(x:%y) (x':%y') = x * y' x' * y
which passes my testsuite for this bug. However, I also tested the
equivalence of same-sign infinities (which I assumed to be a desired
property when I wrote the code) and found that it wasn't working; for
example
Prelude GHC.Real (2:%0) == (1:%0)
False
When I also found that, for example,
Prelude GHC.Real (2:%4) == (1:%2)
False
I figured that (:%) wasn't intended to equate different forms of actually-
equal ratios. So I figured my proposed bug fix would just introduce
another bug, since it, for example, yields
Prelude GHC.Real (2:%0) (1:%0) -- should be False
False
Prelude GHC.Real (2:%0) = (1:%0)
True
which contradicts the non-equality observed above. But then I tried
Prelude GHC.Real compare (2:%4) (1:%2)
LT
Prelude GHC.Real (2:%4) (1:%2)
False
which doesn't make sense(?), and figured I'm probably missing the bigger
picture here. Thoughts?
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2076#comment:5
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2076: rational infinities don't compare correctly to each other
#2076: rational infinities don't compare correctly to each other
-+--
Reporter: uhollerbach | Owner: jeffrey
Type: bug | Status: new
Priority: normal| Milestone: _|_
Component: libraries/base| Version: 6.8.2
Keywords:| Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown |Testcase:
Blockedby:|Blocking:
Related:|
-+--
Comment(by jeffrey):
In libraries/base/GHC/Real.lhs, I added
{{{
instance (Integral a) = Ord (Ratio a) where
{-# SPECIALIZE instance Ord Rational #-}
+ (x:%0) = (x':%0 ) = x0 || 0 x'
+ (x:%0) = (_ :%_ ) = x0
+ (_:%_) = (x':%0 ) = 0x'
(x:%y) = (x':%y') = x * y' = x' * y
+ (x:%0) (x':%0 ) = x0 0 x'
+ (x:%0) (_ :%_ ) = x0
+ (_:%_) (x':%0 ) = 0x'
(x:%y) (x':%y') = x * y' x' * y
}}}
which passes my testsuite for this bug. However, I also tested the
equivalence of same-sign infinities (which I assumed to be a desired
property when I wrote the code) and found that it wasn't working; for
example
{{{
Prelude GHC.Real (2:%0) == (1:%0)
False
}}}
When I also found that, for example,
{{{
Prelude GHC.Real (2:%4) == (1:%2)
False
}}}
I figured that (:%) wasn't intended to equate different forms of actually-
equal ratios. So I figured my proposed bug fix would just introduce
another bug, since it, for example, yields
{{{
Prelude GHC.Real (2:%0) (1:%0) -- should be False
False
Prelude GHC.Real (2:%0) = (1:%0)
True
}}}
which contradicts the non-equality observed above. But then I tried
{{{
Prelude GHC.Real compare (2:%4) (1:%2)
LT
Prelude GHC.Real (2:%4) (1:%2)
False
}}}
which doesn't make sense(?), and figured I'm probably missing the bigger
picture here. Thoughts?
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2076#comment:6
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2076: rational infinities don't compare correctly to each other
#2076: rational infinities don't compare correctly to each other -+-- Reporter: uhollerbach | Owner: jeffrey Type: bug | Status: new Priority: normal| Milestone: _|_ Component: libraries/base| Version: 6.8.2 Keywords:| Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown |Testcase: Blockedby:|Blocking: Related:| -+-- Changes (by jeffrey): * cc: jeffreyjthornton@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2076#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2076: rational infinities don't compare correctly to each other
#2076: rational infinities don't compare correctly to each other -+-- Reporter: uhollerbach | Owner: jeffrey Type: bug | Status: new Priority: normal| Milestone: _|_ Component: libraries/base| Version: 6.8.2 Keywords:| Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown |Testcase: Blockedby:|Blocking: Related:| -+-- Changes (by jeffrey): * owner: = jeffrey * failure: = None/Unknown -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2076#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
