| Re: Strange Bug with numeric double constants [message #14700] |
Mon, 22 March 1999 00:00 |
thompson
Messages: 584
Registered: August 1991
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Senior Member |
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Alex Schuster <alex@rosa.mpin-koeln.mpg.de> writes:
> Hi!
> I just experienced some weird IDL behaviour:
> IDL> help, 1.0d+2.0d
> help, 1.0d+2.0d
> ^
> % Syntax error.
> IDL> help, 1d+2d
> help, 1d+2d
> ^
> % Syntax error.
> Strange, isn't it? There's no problem with byte constants:
> IDL> help, 1b+2b
> <Expression> BYTE = 3
> An additional blank helps:
> IDL> help, 1d +2d
> <Expression> DOUBLE = 3.0000000
> I didn't try IDL 5.2, but it happened with 4.0 and 5.1 on Unix and
> Windows. I guess IDL expects an exponential notation like 1d0, and is
> confused by the nonnumeric plus character.
Wouldn't it be more proper to write these numbers as
IDL> help, 1.0d0+2.0d0
As others have pointed out, IDL is getting confused by putting the +2
immediately after the "d"--it thinks it's part of the exponent. I guess that
IDL usually knows what you meant if you leave the exponent off, but not always
as you found out.
Cheers,
William Thompson
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| Re: Strange Bug with numeric double constants [message #14702 is a reply to message #14700] |
Mon, 22 March 1999 00:00  |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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Alex Schuster wrote:
>
> Hi!
>
> I just experienced some weird IDL behaviour:
>
> IDL> help, 1.0d+2.0d
>
> help, 1.0d+2.0d
> ^
> % Syntax error.
> [...]
I'd just say it's normal. Since '+' or '-' are two allowed characters
in the exponential, IDL wants to interpret everything after '+' as the
exponent, and you are limited to integer exponents here.
Just for fun: if you try
help,1.d*2.d it will work!
Martin.
--
------------------------------------------------------------ -------
Dr. Martin Schultz
Department for Engineering&Applied Sciences, Harvard University
109 Pierce Hall, 29 Oxford St., Cambridge, MA-02138, USA
phone: (617)-496-8318
fax : (617)-495-4551
e-mail: mgs@io.harvard.edu
Internet-homepage: http://www-as.harvard.edu/people/staff/mgs/
------------------------------------------------------------ -------
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| Re: Strange Bug with numeric double constants [message #14709 is a reply to message #14700] |
Mon, 22 March 1999 00:00 |
R.Bauer
Messages: 1424
Registered: November 1998
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Senior Member |
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Alex Schuster wrote:
> Hi!
>
> I just experienced some weird IDL behaviour:
>
> IDL> help, 1.0d+2.0d
>
> help, 1.0d+2.0d
> ^
> % Syntax error.
> IDL> help, 1d+2d
>
> help, 1d+2d
> ^
> % Syntax error.
>
> Strange, isn't it? There's no problem with byte constants:
>
> IDL> help, 1b+2b
> <Expression> BYTE = 3
>
> An additional blank helps:
>
> IDL> help, 1d +2d
> <Expression> DOUBLE = 3.0000000
>
> I didn't try IDL 5.2, but it happened with 4.0 and 5.1 on Unix and
> Windows. I guess IDL expects an exponential notation like 1d0, and is
> confused by the nonnumeric plus character.
>
> Alex
> --
> Alex Schuster Wonko@weird.cologne.de PGP Key available
> alex@pet.mpin-koeln.mpg.de
If you look to the exponent definition it isn't strange because
help, 1d+2
<Expression> DOUBLE = 100.00000
It isn't allowed to use the D to define double more than once in a
definiton of a number.
If you won't use blank to separate the numbers you can use ()
help, (1d)+(2d)
<Expression> DOUBLE = 3.0000000
R.Bauer
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