> > This comment seems wrong:
> >
> > + * However weak implication fails: e.g., "NULL IS NOT NULL" is false, but
> > + * "NULL = ANY(ARRAY[NULL])" is NULL, so non-falsity does not imply non-falsity.
> >
> > "non-falsity does not imply non-falsity"? I suppose one of those
> > negations should be different ...
>
> Earlier in the file weak implication (comments above
> predicate_implied_by) is defined as "non-falsity of A implies
> non-falsity of B". In this example we have NULL for A (non-false) but
> false for B, so that definition doesn't hold. So I think the comment
> is accurate, but I can reword if you have an idea of what you'd like
> to see (I've tweaked a bit in the attached patch to start).
I forgot to update in v8 so attaching v9.
James Coleman
