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Re: ATAN function with two ARGS [message #20280 is a reply to message #20279]

Tue, 06 June 2000 00:00

Ben Tupper
Messages: 186
Registered: August 1999

Senior Member

Ben Tupper wrote:

> In comp.lang.idl-pvwave you write:
>
>> Hello,
>
>> I have bumped into a conflict between the IDL documentation and IDL output.
>
>> From the IDL (5.2) docs, the optional argument Y is described as follows:
>
>> -------START
>> Y
>> An optional argument.
>
>> If this argument is supplied, ATAN returns the angle whose tangent
>
>> is equal to Y/X. If both arguments are zero, the result is undefined.
>
>> ------END
>
>> So I tried the following...
>
>> IDL> help, ATAN(0.0,0.0)
>> <Expression> FLOAT = 0.00000
>
>> Uhoh! Is it me, or is it Monday morning syndrome?
>
>> Ben
>
> When I try the above command, I get
>
> IDL> help,atan(0.0,0.0)
> <Expression> FLOAT = -NaN
>
> IDL> help,/struct,!version
> ** Structure !VERSION, 5 tags, length=80:
> ARCH STRING 'alpha'
> OS STRING 'OSF'
> OS_FAMILY STRING 'unix'
> RELEASE STRING '5.2'
> BUILD_DATE STRING 'Oct 30 1998'
>
> William Thompson
>

The above was sent to me by William Thompson. Below is the version info for
the platform not returning the undefined value.
I've sent notice of this anomaly to RSI.

Thanks,

Ben

IDL> help,!version
<Expression> STRUCT = -> !VERSION Array[1]
IDL> help,!version,/str
** Structure !VERSION, 5 tags, length=40:
ARCH STRING 'sparc'
OS STRING 'sunos'
OS_FAMILY STRING 'unix'
RELEASE STRING '5.2'
BUILD_DATE STRING 'Oct 30 1998'
IDL> help, ATAN(0.0, 0.0)
<Expression> FLOAT = 0.00000

--
Ben Tupper

Bigelow Laboratory for Ocean Science
tupper@seadas.bigelow.org

pemaquidriver@tidewater.net

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[Message index]

		Re: ATAN function with two ARGS By: K. Bowman on Tue, 06 June 2000 00:00
		Re: ATAN function with two ARGS By: Ben Tupper on Tue, 06 June 2000 00:00
		Re: ATAN function with two ARGS By: davidf on Mon, 05 June 2000 00:00
		Re: ATAN function with two ARGS By: Ben Tupper on Mon, 05 June 2000 00:00
		Re: ATAN function with two ARGS By: Ben Tupper on Mon, 05 June 2000 00:00
		Re: ATAN function with two ARGS By: davidf on Mon, 05 June 2000 00:00

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