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Re: -32768 [message #88108 is a reply to message #88104]

Thu, 20 March 2014 14:30

Yngvar Larsen
Messages: 134
Registered: January 2010

Senior Member

On Thursday, 20 March 2014 18:01:01 UTC+1, Karl wrote:
> On Thursday, March 20, 2014 3:24:59 AM UTC-6, Rob Klooster wrote:
>
>> The reason it does not work, is that you first try to define +32768 and then negate the result. Since +32768 can only be expressed as a long, you end up with a long variable. Using fix is a solution, but you could also use the bitwise not operator, if you feel adventurous:
>
>> IDL> a = not 32767
>> IDL> help, a
>> A INT = -32768

Just for completeness of the thread.

(1) A literal short fails here:

IDL> help, -32768S
help, -32768
^
% Integer constant must be less than 32768.

I consider this a bug.

(2) The following silly tricks work as expected:

IDL> help, -32767S-1
<Expression> INT = -32768
IDL> help, 32767S+1
<Expression> INT = -32768

(3) Generalizing to 32- and 64-bits integers:

IDL> help, -2147483648L

help, -2147483648
^
% Long integer constant must be less than 2147483648.

IDL> help, -9223372036854775808LL
<Expression> LONG64 = -9223372036854775808
IDL> help, -9223372036854775809LL
<Expression> LONG64 = 9223372036854775807

Thus, we have the same bug for 32-bit integers, but not for 64-bit!!

IDL> print, !version
{ x86_64 linux unix linux 8.2.2 Jan 23 2013 64 64}

--
Yngvar

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[Message index]

		-32768 By: greg.addr on Tue, 18 March 2014 21:43
		Re: -32768 By: skymaxwell@gmail.com on Tue, 18 March 2014 22:02
		Re: -32768 By: Craig Markwardt on Wed, 19 March 2014 12:17
		Re: -32768 By: Rob Klooster on Thu, 20 March 2014 02:24
		Re: -32768 By: Karl[1] on Thu, 20 March 2014 10:01
		Re: -32768 By: Jim Pendleton on Thu, 20 March 2014 14:11
		Re: -32768 By: Yngvar Larsen on Thu, 20 March 2014 14:30
		Re: -32768 By: chris_torrence@NOSPAM on Thu, 20 March 2014 16:44
		Re: -32768 By: Yngvar Larsen on Fri, 21 March 2014 11:02
		Re: -32768 By: Yngvar Larsen on Fri, 21 March 2014 11:04
		Re: -32768 By: Lajos Foldy on Fri, 21 March 2014 11:16
		Re: -32768 By: Yngvar Larsen on Fri, 21 March 2014 11:39
		Re: -32768 By: Lajos Foldy on Fri, 21 March 2014 12:55
		Re: -32768 By: Dick Jackson on Sat, 22 March 2014 13:20
		Re: -32768 By: Lajos Foldy on Sat, 22 March 2014 13:58
		Re: -32768 By: Dick Jackson on Sat, 22 March 2014 16:56

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