paul c wrote:
> J M Davitt wrote:
>
>> 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.
>
>
>
> i wonder if such postponement could be useful.
>
>
> p
Absolutely; if nothing more, it means that the type declaration
doesn't have to include all the operators one might need.
Received on Wed Jun 21 2006 - 07:36:49 CDT
