Motions 52, 54, 55, 56, 57: YES
I vote YES on motions 52, 54, 55, 56, 57.
I have noted a few things while reading the document, which might be
worth tweaking at a later time:
- The "tightest" mode is defined as returning the hull of the exact set
(rather than just some minimal enclosure of the exact set). This is
possibly too strong. Indeed, as 12.8 points out, the minimal enclosure
is not unique for "implicit" types, so the hull is only one of the many
possible minimal enclosures. This means that 12.10.1 requires that, if
two exact sets are equal, then an implementation shall return the exact
same minimal enclosure, irrespective of the actual values of the inputs.
As a consequence, I believe it is impossible to design a conforming
implementation. (It would be possible if only a minimal enclosure was
required, which is what people actually expect from an implementation.)
- Obviously, the same point holds for 12.12.7, 12.12.8, and 12.12.11. A
simple fix might be to add a variant of "hull_T" that returns the set of
all the minimal intervals, rather than a single one. So definitions
would no longer be "... = hull_T(...)" but "... \in Hull_T(...)".
Similarly, definitions would no longer be "the T-hull of ..." but "a
T-hull of ...". Obviously, this only applies to places where T is not
explicitly required to be a 754-conforming interval type.
- In 12.12.9, the sentence about the rounding of zero is redundant with
the way rounding is defined.
Best regards,
Guillaume