Re: Constructors motion 30 Version 2: small amendment
On 2012-02-07 16:03:08 +0000, John Pryce wrote:
> Vincent
>
> On 7 Feb 2012, at 15:24, Vincent Lefevre wrote:
> >> A NaI by definition is a decorated interval value that can never be
> >> the result of a successful construction, and is used to signal a
> >> construction failure. What NaI values exist will be decided by a
> >> later motion on decorations, but there must be at least one.
> >
> > Isn't NaI a Level 2+ notion only?
>
> I entirely disagree. What is the point of
> - defining decorations at Level 1;
> - saying that only decorated-interval constructors exist;
> - being able to define decorated-interval values -- such as (Empty, ill)
> in my current system -- that can be used for the desired diagnostic
> purpose, i.e. as NaI values;
The problem is that NaI doesn't appear in the Level 1 definition
(Table 1). Well, I've just noticed that it doesn't appear in
the Level 2 definition either, so that's a problem too. And
NaI seems to be regarded as of the same type as bare intervals
(see Section 3.1, where NaI is mentioned, but nothing about
decorations). It would be better to say (Empty, ill) until there
is a proper NaI definition (for instance, what about the status
of decorated intervals of the form (non-Empty, ill)?).
--
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 / AriC project (LIP, ENS-Lyon)