[stdinterval] Comments on the Interval Standard Proposal
Gabriel Dos Reis
gdr at integrablesolutions.net
Sun Oct 1 01:58:58 PDT 2006
Sylvain Pion <Sylvain.Pion at sophia.inria.fr> writes:
 Guillaume Melquiond a écrit :
 >> 26.6.4 interval member functions
 >>
 >> whole();
 >>
 >> I do not see a definition of the static member function whole().
 >> I am particularly interested in what whole().lower() et.al. means.
 > There is a definition in the proposal saying that "whole" returns
 > [inf,
 > +inf]. Anyway, there was some discussions on the list and now "whole" is
 > only defined as returning an interval containing all the real numbers.
 > There is no difference with the older definition for a 754based
 > efficient implementation, but the function can now be defined on an
 > arithmetic without infinities.
 > Concerning the "lower" and "upper" members, I have fixed their
 > definitions along the lines of the "inf" and "sup" functions, so that
 > they return the corresponding infinities for unbounded intervals. When
 > infinities are not available, the behavior is implementationdefined.

 For implementations which do not support infinity, how do you check if
 an interval is bounded ? Currently we can't.
Hmm, I'm unclear about this one. If the implementation does not
support infinity, does not it follow all intervals are bounded?
 What about adding functions like:
 is_positively_bounded(interval<T>), and
 is_negatively_bounded?
 Or something like that.

 Even for cases where infinities are supported, they can be more
 convenient than testing like:
 x.upper() == numeric_limits<double>::infinity()
Yes.
 Gaby
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