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On 11-Nov-06, at 11:29 PM, Chongkai Zhu wrote:

> Hi,
>
> I think the idea of this srfi is good. But the current reference
> implementation is poor. Would the author provide an implementation
> that is a rewrite of srfi-69's reference implementation but do
> apply all the parameters?

The size parameter is easy to implement (it is already supported by
the SRFI 69 implementation).  The min-load and max-load parameters
are not too difficult to implement, you have to store the min-load
and max-load parameters in the <srfi-hash-table> record and resize
the hash-table on an insertion when the load exceeds the max-load,
and on a deletion when the load is less than the min-load.

It is impossible to write a portable and complete implementation of
the weak-keys and weak-values parameters because weak references are
not standard.  In implementations of Scheme which do not support weak
references the garbage collector has to be modified to implement
them.  The situation is similar to the implementation of the eq? test
parameter (i.e. eq?-hash-tables) which requires modifications to the
garbage collector for an efficient implementation (by hashing on the
object address).

If you are interested in implementing all the features fully (and
more) I suggest you look at their implementation in the Gambit
system.  The garbage collector is in the file lib/mem.c and the hash
table procedures are defined in the file lib/_system.scm .

Marc

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