[std-interval] Mathematical relations and default initialization

[Dr John Pryce]

Dear all

At 09:21 14/09/06, Frédéric Goualard wrote:
>* Default initialization
>I see on page 15 that the default constructor creates an empty interval.
>  At some point in the discussion, Sylvain gave 6 possible ways of
>implementing this constructor:
>
>1- no default constructor at all
>2- [0,0]
>3- empty
>4- whole
>5- uninitialized tag
>6- see below (something a la "singular iterator")
>
>Possibility 4 was brushed away from the start, and the remaining
>possibilities heavily debated. In my opinion, it makes sense to have the
>default constructor return "whole" since interval arithmetic is often
>used in processes that try to gain some information on the possible
>value of a variable (that is, we start from a wide interval and narrow
>it down to some reasonably small one).

I am delighted that someone else takes this view. 
The ISL team came down in favour of returning 
"whole" many months ago, for exactly the reason you cite.

Regards

John Pryce
Dr John and Mrs Kate Pryce
142 Kingshill Rd
Swindon, Wiltshire SN1 4LW
UK
Tel (+44)1793-331062