I agree with just about everything you wrote.  I only have two minor
quibbles and they may merely be restatements of what you meant.

--- Rob Kinyon <[EMAIL PROTECTED]> wrote:

> Overriding the operators in a generic way so that you have
> to have an exact type match before you compare values also, 
> imho, shouldn't be that hard. So, for the relational calculus,
> you can have very strong typing.

Minor nit:  we're discussing to the relational algebra and not the
relational Calculus (unless the topic changed and I wasn't paying
attention.  I wouldn't be surprised :)

> > * The domain of acceptable values (potentially infinite)
> > * Selectors to cast to and from the value
> > * Operators and their behaviors
> I would argue that you don't have selectors, by default. You
> should have to explicitly add a selector. Otherwise, into
> C-land you will go, my son!

I'm not entirely sure, but I think we agree here.  You have to have, at
minimum, one selector for each new datatype if for no other reason than
to cast a string to your new data type.  Otherwise, your data types
would only be constants because you would have no way of assigning a


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