[std-interval] Revised document available

[Gabriel Dos Reis]

Guillaume Melquiond <guillaume.melquiond at ens-lyon.fr> writes:

[...]

| As a consequence, I feel that we should avoid standardizing behavior for
| floating-point values that are not mandated by the C++ standard,
| whenever possible. That's why infinite and NaN are mentioned only in the
| few places where we felt it could be useful to take them into account.
| The behavior is left undefined in the other places. In particular, I
| don't believe it is actually useful to define the behavior of
| interval(NaN,NaN). If it is left undefined, people will not have any
| incentive to use it.

yes, be prepared to justify why the standard library specify
internal(NaN, NaN) when it does not require what NaN does.

A way out of it is to key the semantics on numeric_traits<>.

-- Gaby