2012/2/16, Vincent Delecroix <20100.delecr...@gmail.com>:
> 2012/2/11, Nicolas M. Thiery <nicolas.thi...@u-psud.fr>:
>> On Sat, Feb 11, 2012 at 12:05:49PM +0100, Florent Hivert wrote:
>>> > Together with the language-team, we decided to implement a
>>> > LazyEnumeratedSet (see my patch in the queue) which takes as input an
>>> > iterable (finite or infinite) and mimic a set which contains the
>>> > element of the iterable. It is very useful when we do not want to
>>> > implement a specific class... What do you think of it ?
>>> >
>>> > On the other hand, I'm a bit disappointed as it is not possible to
>>> > pickle an iterator and hence my new class does not pass the TestSuite.
>>> > Any idea ?
>>>
>>> I think this is a good idea to have this feature for the casual user but
>>> that
>>> it should not be used in the code. The reason are:
>>> 1 - The set will not be picklable;
>>> 2 - The usage of tee is likely to leak a lot of memory;
>>> 3 - For programmer, I don't think it is a big save compared to subclass
>>> and
>>> implementing the Cardinality and __iter__ methods. Please have a
>>> look it
>>> some methods couldn't be lifted in the category EnumeratedSet.
>>> If you agree, as a consequence, you should add a big warning at the
>>> beginning
>>> of the file.
>>>
>>> Finally, may I suggest the alternative name EnumeratedSetFromIterator ?
>>
>> We discussed this with Vincent over the phone: I pointed him to the
>> combinatorial_class_from_iterator decorator implemented in
>> class_from_iterator.patch; he volunteered to refactor it as
>> enumerated_set_from_iterator. Note that, as a decorator over an
>> existing function which produces an iterator, it's picklable.
>>
>> I think it's reasonable to use it in code for implementing little
>> functions that returns a set, the main use of which will be to iterate
>> over.
>>
>
> This is now #12518.
>
> Following Florent, I removed ._cardinality attribute and simplify
> everything. I also add an implementation of a cache which allows the
> iterator to be used only once (see sage.misc.iter_with_cache).
>
> I get trouble with TestSuite which only works when elements of the set
> have parents. In particular it does not work in the following case
> {{{
> sage: from sage.sets.set_from_iterator import EnumeratedSetFromIterator
> sage: E = EnumeratedSetFromIterator(graphs,
> category=InfiniteEnumeratedSets())
> sage: TestSuite(E).run()
> }}}
> Actually the above example leads to an infinite loop.
>
> I wrote an implementation of the decorator for functions (which
> works!) but I'm not sure about what to do for the case of methods. Any
> idea ? As soon as the decorator is ready, the ticket will need review.
>
Trying to put my patch a little bit higher in the queue, I noticed the
presence of the patch class_from_iterator.patch (which does not
commute with mine as I basically deprecate what it did). There is no
author, if there is no candidate for the ownership I will simply
remove it...
Vincent
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