Re: [Vala] [LigGee] remove_all behavior at removing same items

["Didier \"Ptitjes\"" <ptitjes free fr>]

Hi Tomaž!

Quikee wrote:
> In what way should remove_all work in case of removing the same items.
> Currently there is an inconsistency in this behavior from remove_all
> on AbstractCollection and the implementation in ArrayList.
> The AbstractCollection implementation will call remove for every
> element which will in case of n same items in list 1 and m same items
> in incoming list 2 remove n-m items.
>
> For example:
> list1 has items 1,1,1,1,1 and list2 has items 1,1,1
> after remove_all in list1 would remain items 1,1
>
> The implementation on ArrayList will always remove all items from the
> list if the incoming list has such an item.
> So in the same example as above list1 after the call would not have any items.
>
> I have looked also how Java's ArrayList behaves in such a case and it
> did behave in a different way as above. The Java's ArrayList treated
> the incomming collection as a set and did delete only one element from
> the list1.
> So the example would look like this:
> list1 has items 1,1,1,1,1 and list2 has items 1,1,1
> after remove_all in list1 would remain items 1,1,1,1
>
> Which of this behavior would you prefer?

That's a good thing you point here. IMHO we should explicit API
contracts in the collection interfaces.

I would prefer that remove is said to remove the first element.
And that remove_all removes every element instances. IMHO this will
enable to respect the same API contract for multi-sets.

As you can read in Apache Commons Collections, which build upon and
derives from Java Collections, their Bag interfaces explicitly override
the defined behavior for contains|remove|*All methods. [1]

Thus I would prefer if our Collection interface already defines a such
API contract: remove_all removes all the element occurrences. In simple
sets, it would obviously remove only one instance.

Best regards, Didier.

[1]
http://commons.apache.org/collections/apidocs/org/apache/commons/collections/Bag.html#removeAll(java.util.Collection)