On to Hydro

[Tyler Close]

Markm wrote:
> Having NaNs be larger than all non-NaNs, including positive
> infinity, is
> surprising too.

Yes, well, I've got a two-dimensional container and
three-dimensional(?) data, so some contortion will have to take place.
You can also think of it as "put them at the end", rather than "make
them larger than everything".

I don't want to divert the conversation too much, but could anyone
quickly tell me why division by 0 is even permitted (instead of
throwing an exception)? Are there algorithms in which it makes sense
to divide a number by zero? If so, why is division of an integer by
zero an exception?

> NaNs, however, are an edge condition.
> Subsets, subtypes,
> preferences, causality -- the universe is rife with partial
> orderings, and
> partial orderings are the more general category.

True, but maybe we need some other concept for them other than "less
than". Less than implies that I can sort. I can't sort with only a
partial ordering. I can't even search with only a partial ordering. I
think you'll have to upgrade the "<" operator to at least strict weak
ordering, though I'll push for total ordering.

I think the solution might be that we don't provide any 'automatic'
comparison operators, and just map them all into method names.

Operator   Method     Ordering
--------   ------     ---------
   <       before     total or strict weak
   <=      within     partial
   >       after      total or strict weak
   >=      includes   partial

Tyler


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