Re: Motion P1788/M007.01_NaI: Discussion period begins
Jürgen Wolff v Gudenberg schrieb:
Arnold Neumaier schrieb:
The motion was for having a unique NaI, in which case the propagation
rule is OK.
But I think there should either be no NaI (which I'd favor),
or there should be NaI with payload.
what do you propose for illegal construction ?
1. return emptyset
2. return emptyset with payload
3. return emptyset and set a sticky flag
4. just set the flag
5. raise an exception
6. terminate
I think in section 2.3 remarks Vienna proposal favors option 2.
which I consider equivalent to a unique NaI
Option 2 is _not_ equivalent with a unique NaI since there may
be different payloads. It is approximately equivalent with having
many NaI, namely one for each allowed payload that does not
represent the ordinary empty set..
Ordinarily, an illegal construction contains no number, hence
can be treated as empty set in arithmetic expressions.
But ''missing value'' would be treated differently in max and min,
so if we want to support this, we need to distinguish Empty from
NaI with payload.
In any case, the ordinary Empty should propagate very fast, while
it is acceptable that Empty/NaI with payload propagates slowly.
Arnold Neumaier
Juergen
Thus I think the motion should not be supported.
To prepare for a possible NaI with payload and to estimate its
likely cost, those interested in having NaI should, as John
Pryce suggested in another mail, collect the desired uses for
NaI and which propagation rules these uses imply.
Arnold Neumaier