Re: Motion 13

[Ulrich Kulisch <Ulrich.Kulisch@xxxxxxxxxxx>]

Ian McIntosh schrieb:
> Detecting uninitialized variables is one of the primary uses of 754's 
> signaling NaNs. In an IA implementation based on 754, the interval 
> [SNaN, SNaN] would be the equivalent. I suppose the corresponding name 
> would be SNaI. Uninitialized variables are one of programming's 
> greatest evils, and SNaI would be better than silently using empty or 
> entire or [0, 0].
Would'nt  [SNaN, SNaN] be an appropriate encoding for the empty set?
> - Ian McIntosh IBM Canada Lab Compiler Back End Support and Development
>
>
> Inactive hide details for Vincent Lefevre ---05/07/2010 04:55:57 
> AM---On 2010-05-05 18:40:08 +0200, Ulrich Kulisch wrote: > ThiVincent 
> Lefevre ---05/07/2010 04:55:57 AM---On 2010-05-05 18:40:08 +0200, 
> Ulrich Kulisch wrote: > This could be a possible use for the empty set
>
>
> From: 	
> Vincent Lefevre <vincent@xxxxxxxxxx>
>
> To: 	
> Ian McIntosh/Toronto/IBM@IBMCA
>
> Date: 	
> 05/07/2010 04:55 AM
>
> Subject: 	
> Re: Motion 13
>
> ------------------------------------------------------------------------
>
>
>
> On 2010-05-05 18:40:08 +0200, Ulrich Kulisch wrote:
> > This could be a possible use for the empty set:
> > Occasionally it happens in programming that a variable is used
> > before a definite value has been assigned to it. This is a terrible
> > error in interval arithmetic and should be avoided by checking for
> > it. A solution could be to set every variable at definition to be
> > the empty set.
>
> It could be NaI if defined. Or it could be the entire set: this would
> allow to correctly handle variables that should have been initialized
> to some value (or interval) but this was forgotten, but programming
> errors (such as typos in variable names) may not be detected.
>
> --
> Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
> Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)


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Prof. Ulrich Kulisch

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