[r6rs-discuss] Unicode issues

Thomas Lord lord at emf.net
Wed Aug 29 23:00:41 EDT 2007


Aubrey Jaffer wrote:
> Not so!  If you use records to specify the new type, then EQV? won't
> work on these new characters.  States r5.97rs-lib section 6.1
> Mutability and equivalence of records:
>
>     * If obj1 and obj2 are both records of the same record type, and
>     are the results of two separate calls to record constructors, then
>     eqv? returns #f.
>   

Oh my goodness.  That's very, very bad.   That reifies an execution
model in a particularly unforgivable way.

I was just thinking, earlier today, that R6 blows it by introducing
intentional types when the only real demand was for user-defined
disjoint types.   I was thinking of libraries but the same design
pattern issue relates to records.

New rule: shun opaque types!  Extensional types only!

Sigh.

-t




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