[Haskell-cafe] Maybe a compiler bug?

[Rafael Gustavo da Cunha Pereira Pinto]

Specifically for this code:

gTst3 right left = if (lr > ll)  then  False else True
			where lr = length (right ! 2)
			      ll = length (left ! 2)

why don't you just negate the condition, like:


gTst3 right left = (lr <= ll)
			where lr = length (right ! 2)
			      ll = length (left ! 2)




2009/1/5 Murray Gross <mgross21 at verizon.net>

>
>
> No unsafe perform (except what may be hidden in trace), nothing, fancy, no
> gimmicks (very pedestrian, even heavy-handed) code. Complete code is
> attached (I don't have smaller snippets, because I just discovered the
> problem).
>
>
>
> Best,
>
> Murray Gross
>
>
>
>
> On Mon, 5 Jan 2009, Luke Palmer wrote:
>
>  On Mon, Jan 5, 2009 at 4:34 PM, Murray Gross <mgross21 at verizon.net>
>> wrote:
>>
>>
>>> When using any of -O, -O1, -O2 with the Debian binary build of GHC 6.6,
>>> trace shows that the expression
>>>
>>>      if (lr > ll)  then  False else True
>>>
>>> is (at least partially) evaluated, but the value returned is always True,
>>> even though trace reports that (lr > ll) is True. When I use only the
>>> native
>>> code generator (without optimization), the correct value (False) is
>>> returned.
>>>
>>> Further detail and complete code on request.
>>>
>>
>>
>> Of course!  This is obviously incorrect behavior.  Are you doing any
>> unsafePerformIO?  Please, complete code (minimal test case if possible,
>> but
>> don't let that stop you).
>>
>> Luke
>>
>>
>>
>>
>>
>>>
>>> Best,
>>>
>>> Murray Gross
>>> _______________________________________________
>>> Haskell-Cafe mailing list
>>> Haskell-Cafe at haskell.org
>>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>>
>>>
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>


-- 
Rafael Gustavo da Cunha Pereira Pinto
Electronic Engineer, MSc.
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