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Re: differences idl5.5 and idl5.6 [message #34075 is a reply to message #34074]

Wed, 19 February 2003 08:56

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Reimar Bauer wrote:
>
> Dick Jackson wrote:
>> "Reimar Bauer" <R.Bauer@fz-juelich.de> wrote in message
>> news:3E539FE4.4000801@fz-juelich.de...
>>
>>> Hi,
>>>
>>> today I found a difference in handling infite numbers by the new
>>
>> version.
>>
>>>
>>> IDL 5.6
>>>
>>> IDL> a=1./0 &print,a,fix(a)
>>> Inf -32768
>>>
>>>
>>> IDL 5.5
>>>
>>> IDL> a=1./0 &print,a,fix(a)
>>> Inf 0
>>>
>>>
>>>
>>> So I can't say which is right both results are terrible.
>>>
>>> Now it is totally clear that this case must be tested.
>>
>>
>> I don't see any change in behaviour on Windows 2000 Pro; in 5.4, 5.5 and
>> 5.6, I get these identical results:
>>
>> IDL> a=1./0 &print,a,fix(a)
>> Inf 0
>> % Program caused arithmetic error: Floating divide by 0
>> % Program caused arithmetic error: Floating illegal operand
>>
>> Cheers,
>> --
>> -Dick
>>
>> Dick Jackson / dick@d-jackson.com
>> D-Jackson Software Consulting / http://www.d-jackson.com
>> Calgary, Alberta, Canada / +1-403-242-7398 / Fax: 241-7392
>>
>>
>
> Thanks Dick,
>
> then it seems to be a bug on linux and aix
>
> on aix the result is a bit more different,
> IDL> a=1./0 & print,a,fix(a)
> Inf -1
>
> I would prefer as result NaN!

Hmm. Wouldn't the integer form of infinity still be infinite? If you think the value of
some variable may be infinite, how come you don't test the value _before_ using it in an
intrinsic function (e.g. FIX()) ?

I.e.

IF ( FINITE( a ) ) THEN a = FIX( a ) ELSE a = !VALUES.F_NAN

And from the IDL docs, it would appear that there is no such thing as an integer infinity
or nan (in IDL at least).

paulv

--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
Ph: (301)763-8000 x7274
Fax:(301)763-8545

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[Message index]

		Re: differences idl5.5 and idl5.6 By: R.G. Stockwell on Wed, 19 February 2003 10:17
		Re: differences idl5.5 and idl5.6 By: K. Bowman on Wed, 19 February 2003 09:26
		Re: differences idl5.5 and idl5.6 By: Paul Van Delst[1] on Wed, 19 February 2003 08:56
		Re: differences idl5.5 and idl5.6 By: R.Bauer on Wed, 19 February 2003 08:33
		Re: differences idl5.5 and idl5.6 By: Dick Jackson on Wed, 19 February 2003 07:54
		Re: differences idl5.5 and idl5.6 By: R.Bauer on Thu, 20 February 2003 01:01

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