> On 28 Feb 2015, at 15:41, Philip Hazelden <philip.hazel...@gmail.com> wrote:
>
> I'm trying to represent something of the form "I've chosen one member of this
> group, three members of that group, and nobody from the other group". A Bag
> seems right for this, except that if I want to get the list of groups, it
> doesn't seem to include the one with nobody:
>
> > Bag.new-from-pairs('a' => 0, 'b' => 3)
> bag(b(3))
> > my $b = BagHash.new()
> BagHash.new()
> > $b<a> = 3
> 3
> > $b
> BagHash.new(a(3))
> > $b<a> = 0
> 0
> > $b
> BagHash.new()
>
> I was hoping for something like Python's Counter:
>
> >>> Counter({'a': 0, 'b': 3})
> Counter({'b': 3, 'a': 0})
> >>> b = Counter()
> >>> b['a'] = 2
> >>> b
> Counter({'a': 2})
> >>> b['a'] = 0
> >>> b
> Counter({'a': 0})
>
> I'm wondering if anyone has any bright ideas related to this. Two things come
> to mind for myself: I could subclass Bag (or create a new implementation of
> Baggy), but I'm not entirely sure how I'd do so sensibly (i.e. without
> reimplementing basically the whole of Bag - operators, initializers,
> stringifiers...); or I could create a new class which basically contains
> nothing but a list and a bag whose keys are elements of the list.
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An interesting thought for the non-mutable cases of Set, Bag and Mix.
For the mutable cases (SetHash, BagHash, MixHash), setting the element to 0, is
effectively deleting it.
For the non-mutable case, I guess we could argue that *if* you specified it, it
should exist as such.
Will ponder about this…
Liz
