So FWIW, I think the interface I'd like to use is one where there's nothing
special about 0 values. You can put them in and they'll stay there, and if
(+) results in an element with value 0, that stays there too. But if you
ask for the value of something which doesn't have an explicit value, you'll
get 0 instead of Any.
This seems like a valuable thing to have, even if it's not the interface of
Bag itself. (I agree that there's something strange about a Bag containing
no items yet not being empty.)
That said, in this specific case a Hash or EnumMap should be pretty okay,
except that I want non-stringy keys. I've finally discovered object hashes,
so I think I'll be able to make those work.
(In case anyone stumbles upon this while trying to get non-stringy keys:
the syntax :{} constructs a hash whose keys can be arbitrary objects, not
just strings. So :{ 1=>2 }<1> returns Any, because the hash contains the
number 1, not the string "1". At least that's my current understanding.)
On Sun, Mar 1, 2015 at 9:01 AM, Elizabeth Mattijsen <l...@dijkmat.nl> wrote:
>
> > On 01 Mar 2015, at 02:01, Darren Duncan <dar...@darrenduncan.net> wrote:
> >
> > On 2015-02-28 3:27 PM, Elizabeth Mattijsen wrote:
> >> 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…
> >
> > If you're going to support that alternative, it should still be easy for
> one to get the behavior where the non-mutable cases don't contain elements
> with a count of zero. Zeros can easily arise when doing operations like
> set difference or intersection etc, and we would want consistency between
> values that arise that way versus ones explicitly selected with a literal.
> -- Darren Duncan
> >
>
> The pondering has been cleared up by TimToady:
>
> http://irclog.perlgeek.de/perl6/2015-03-01#i_10199408
>
> so (a=>0).Bag will continue to yield ().Bag.
>
>
>
> Liz
