Re: Motion 13

[Ian McIntosh <ianm@xxxxxxxxxx>]

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].

- Ian McIntosh IBM Canada Lab Compiler Back End Support and Development


Vincent 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.

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