Re: Remarks on Motion 11
Frédéric Goualard, Marco Nehmeier & P1788
On 24 Jan 2010, at 21:00, Frédéric Goualard wrote:
> Thank you very much for taking the time to write Motion 11 and submit it
> to P1788. I believe that what you call "Reverse Interval Operations" are
> very important and should find their place in the upcoming interval
> standard.
>
> I have, however, one regret and one remark:
> The regret is that your motion only concerns itself with basic
> operations, which is not reflected by its title. Why not consider
> reverse cosine, reverse sine, ... ? Constraint programming, for example,
> cannot make do with reverse multiplication and reverse division only.
Marco, I also am glad you have submitted this motion, but I agree with Frédéric. Arnold Neumaier in the Vienna document proposes -= if I count correctly - 14 functions/operations to be provided in reverse mode. Anyone who agrees with the general concept of "reverse operation" is probably happy to vote for the whole of Arnold's list (give or take one or two, to be argued case by case). As a friendly amendment I suggest: include all 14 (or whatever) in your motion, and phrase it on the lines of Juergen's motion 10.
I feel your document could be clearer on what the motion *is*, i.e. what are we voting for? At present this is hidden within the two Definitions, which say "… should …". State the motion separately, and say "shall", not "should".
> One remark: I believe that Corollary 1 is false---which should address
> the question raised by Nate Hayes' mail. For example, take
>
> A=[0,2]
> B=[-1,1]
> C=[1,1]
Good point. Thanks for clarifying it. It's the order in which "hull" and "intersect" are done that makes the difference, I think.
Best wishes
John Pryce