#3304: define gcd 0 0 = 0
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Reporter: stevec | Owner:
Type: proposal | Status: closed
Priority: normal | Milestone: 7.2.1
Component: libraries/base | Version: 7.1
Resolution: fixed | Keywords:
Testcase: | Blockedby:
Difficulty: Unknown | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown |
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Comment(by daniel.is.fischer):
Thanks.
The only feasible ways to throw an exception I see are
{{{
case {- abs $ -} gcd' (abs x) (abs y) of
g | g < 0 -> overflowError
| otherwise -> g
}}}
or
{{{
let x' = abs x
y' = abs y
in if x' < 0 || y' < 0 then overflowError else gcd' x' y'
}}}
In the former case, the `abs` on the result would be much better, or you'd
get an overflowError half the time when one argument is minBound for
signed bounded types, which would be hard to predict and understand. In
the latter case, you'd get consistent and predictable exceptions, but
unnecessarily many, in my opinion.
I would prefer to not throw an exception, however, because often you can
carry on perfectly well with a negative result.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3304#comment:16>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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