comp.lang.idl-pvwave archive: archive

Home » Public Forums » archive » -32768

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: -32768 [message #88126 is a reply to message #88122]

Fri, 21 March 2014 11:16

Lajos Foldy
Messages: 176
Registered: December 2011

Senior Member

On Friday, March 21, 2014 7:02:08 PM UTC+1, Yngvar Larsen wrote:

> For literals, I agree that this might be regarded as dubious. But in general, the fact that N-bit integer arithmetic is silently wrapped modulo 2^N should be regarded as semantically well defined. If not, I believe a serious performance hit would result.

The C standard guarantees modulo 2^N arithmetic for unsigned integers only. For signed integers, the behavior is undefined.

-32768 is a funny number. Did you know that its absolute value is negative?

IDL> help, abs(-32767-1)
<Expression> INT = -32768

This is the consequence of the asymmetric representation of integers, 32768 can not be represented as an int and there is no NaN for integers.

regards,
Lajos

Report message to a moderator

[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

Previous Topic:	Killing Widget Objects
Next Topic:	How to choose the pixels along a curve in an image

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sat Oct 11 07:18:01 PDT 2025

Total time taken to generate the page: 2.72101 seconds