Re: relations aren't types?

"Marshall Spight" <mspight_at_dnai.com> wrote in message <news:y8_Gb.205873$_M.909925_at_attbi_s54>...

> I say: why bother with the conversion? Why not just declare the two
> cases as identical? I don't see any advantage to distinguishing between
> the two cases. (Maybe there is an implementation advantage.)

Perhaps if x and y have interdependent integrity rules, such as they must have the same sign or the point must be within a certain distance of (0, 0) or whatever. Such rules might be clearer with an encapsulated data type instead of leaving them up to rules on the tuples.

--
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