Re: First Impressions on Using Alphora's Dataphor

On Sat, 28 Aug 2004, Rene Hartmann wrote:

> I would rather suggest using a system-defined comparison operator, which
> could be based on the internal representation of a type.
> This operator must only be consistent with the equality operator, so that
> if A = B then A <= B must also evaluate to true. Since the operator
> is only used internally for purposes of duplicate elimination, there are
> no special requirements for it.
>

OK, I must admit that things are not as easy as I thought first. I thought a comparison function which first calls the user-provided equality operator and then compares the byte representation would do, but this could lead to a situation where A < B < C but A = C.

So it seems that if the user provides an equality operator, s/he must also provide <=.

But I think a user-provided equality operator is rarely possible, because equality could be based on a possible representation, and <= could too.

--
Rene´ Hartmann