Tony D wrote:
> J M Davitt wrote:
>
>>CJD calls them type constraints; they define the set of values
>>that constitute the type. Types are named, so the sets are named.
>>
>>The only thing I'd argue about in Cimode's definition is that
>>operators are part of the data type. In fact, D+D make the point
>>that the declaration of operators is orthogonal to the declaration
>>of types -- given that the types are extant before the operators.
>>
>
> Before I go, one last point; I'm not sure how the declaration of
> operators can be *completely* orthogonal to type declaration; after
> all, there's not much point in declaring a type if you can't actually
> do anything with it. I understand that not all operators may be defined
> when the data type is first introduced, but at least some operators
> (equivalence definitely) will have to be there pretty much from the
> get-go.
The idea gave me pause, too. They emphasize that operators need not
be declared as part of the type declaration. Yes, the RM requires
an operator that can distinguish values of given types -- but that
operator need not be declared before the type appears in an attribute.
The selector operator and the /THE_/ operators are the notable
exceptions: they are implicitly declared in the type declaration, IIRC.
And, yes, you're right: you can't actually do much with only those.
Received on Tue Jun 20 2006 - 23:08:18 CDT
