Re: Motion P1788/M0006.04_Level_2_Multi-format NO
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Dear John,
John Pryce wrote:
[ part snipped ]
>> BTW, I see this as an error (or some ambiguity) in the position paper,
>> which seems to talk about Level-3 issues in a Level-1 section.
>
> I am sorry if the wording of the Motion 6 paper has been ambiguous. But
> anyone who thinks this [-oo,-oo] and [+oo,+oo] business has ANYTHING to
> do with level 3 issues is completely wrong.
>
> As I wrote privately to Frédéric yesterday:
>> On motion 6, however, you are mistaken. The reference to [-oo, -oo]
>> and [+oo, +oo] is in the Level 1 description. It simply says that as a
>> matter of mathematical notation, these are semantically invalid
>> sequences of symbols. That has no connection with, for instance, what
>> should be returned by a constructor call such as
>> interval(-Inf,-Inf)
> ... which is (I believe) a level 2 issue yet to be decided ...
>
> or what level 2 datum, if any, is represented by a level 3 interval
> object if its fields (xlo,xhi) represent the inf and sup of an interval
> and happen to hold xlo = xhi = -Inf ;
> ... which is a level 3 issue yet to be decided.
>
> In the context of the motion 6 paper, the relevant sentence is deeming
> [-oo, -oo] and [+oo, +oo] to be invalid math notation for an interval in
> the same way as ["tuesday", "camembert"] is invalid.
I am still confused here. I understand your point regarding the various
levels (also raised by Prof. Neumaier in one of his recent mails).
However, if, say, [-oo, -oo] is considered an invalid *notation* that
shall not be identified with the empty set, what are our options to
having it handled when time comes? I believe it can either be identified
with some "exceptional" interval (viz. NaI), or the program has to
"break" (flag raising, exception raising, or whatever is available in
the programming language considered). Both ways do not make me happy.
Hence my NO vote on this motion; I cannot foresee a satisfying way of
defining the levels that are not the subject of this motion given what
would be defined in the levels it considers. I would be more than happy
to be proved wrong, in which case I would gladly reverse my vote.
F.
- --
Frédéric Goualard LINA - UMR CNRS 6241
Tel.: +33 2 51 12 58 38 Univ. of Nantes - Ecole des Mines de Nantes
Fax.: +33 2 51 12 58 12 2, rue de la Houssinière - BP 92208
http://goualard.frederic.free.fr/ F-44322 NANTES CEDEX 3
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