[armedbear-devel] tentative patch: extensible sequences (following the same protocol as SBCL)

[Alessio Stalla]

On Tue, Mar 2, 2010 at 11:27 AM, Tobias C. Rittweiler <tcr at freebits.de> wrote:
> Alessio Stalla <alessiostalla at gmail.com>
> writes:
>
>> Greetings everyone,
>>
>> I'm happy to announce that I have a preliminary version of
>> user-extensible sequences working on ABCL, following the protocol
>> proposed and implemented by Christophe Rhodes on SBCL
>> ("User-extensible sequences in Common Lisp",
>> http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.65.1604&rep=rep1&type=pdf).
>> This includes:
>>
>> - the possibility for the user to write subclasses of CL:SEQUENCE
>> - all functions operating on sequences have a corresponding generic
>> function in the SEQUENCE package that is called on user-defined
>> sequence types, and for which the user can write methods to implement
>> his/her custom sequences
>> - make-sequence works with user-defined sequences (using
>> sequence:make-sequence-like as in SBCL)
>> - mop::class-prototype has been added (as a tiny wrapper around
>> mop::allocate-instance)
>> - iterating over user-defined sequences integrated with LOOP
>> (untested, but should work as our loop implementation is derived from
>> CMUCL like SBCL's)
>> - MAP and MAP-INTO should work unchanged
>>
>> limitations/things missing wrt. SBCL (that I know of):
>>
>> - no integration with DOSEQUENCE
>
> I have spent some time on thinking about a good middle layer on top of
> sequences and what I came up with so far is at
>
>  http://common-lisp.net/project/sequence-iterators/
>
> It's supposed to hook into extensible sequences where available though I
> haven't come around of doing so for sbcl.
>
> So if you're looking for a mid layer, I think cloning those interfaces
> might make sense.

Looks very interesting, thanks. Especially the with-sequence-iterator
macro, which is higher-level than SBCL's and more user-friendly (a
SBCL sequence iterator is something like 3 objects + 6 functions). So,
I will certainly clone those interfaces, and maybe even steal some
code ;)

Alessio