On 6/26/06, Andre van Tonder <xxxxxx@now.het.brown.edu> wrote:

> I like the operational semantics in the SRFI, since it may be less ambiguous
> than the alternative declarative approach.
>
> As corrobrating evidence, I can mention the syntax-case implementation in
> SRFI-72.  That implementation satisfies declarative descriptions of
> hygiene.  However, the implementation technique is based on an "implicitized"
> version of explicit renaming, not marking/substitution.  There are some highly
> obscure corner cases where it behaves differently from the marking algorithm,
> while still satisfying hygiene.  I have to recheck, but I think these
> ambiguities should be resolved by specifying the algorithm as is
> done here (though perhaps a little more detail might be required).

I think the trick is to make an unambiguous declarative specification.

David