If the collection implements = using the objects it holds then you need to consider at least some of them in the hash calculation. I can't conceive a hash calculation for this case independent of the contents (well, just hardcode a number but this will lead to always collide if used as a key in a hashed collection).
I'm with Levente here, I think the hash implementation is reasonable. And I wouldn't use a mutable object as key in a hashed collection. On Fri, Oct 9, 2015 at 11:07 AM, Esteban Lorenzano <esteba...@gmail.com> wrote: > but that’s an error, I think. > a collection has to have always same hash… no matter its size (because is > not an array) and no matter his elements. > > > > On 09 Oct 2015, at 15:21, Levente Uzonyi <le...@elte.hu> wrote: > > > > You simply don't modify _objects_ which are used as keys in hashed > collections. Or if you do so, you'll have to deal with the consequences > yourself. > > > > Levente > > > > On Fri, 9 Oct 2015, Esteban Lorenzano wrote: > > > >> Hi, > >> > >> Can anyone explain me how this is correct? > >> > >> Collection>>#hash > >> "Answer an integer hash value for the receiver such that, > >> -- the hash value of an unchanged object is constant over time, > and > >> -- two equal objects have equal hash values" > >> > >> | hash | > >> > >> hash := self species hash. > >> self size <= 10 ifTrue: > >> [self do: [:elem | hash := hash bitXor: elem hash]]. > >> ^hash bitXor: self size hash > >> > >> > >> I mean… a hash that changes when I add elements to the collection… how > can this work? > >> > >> Esteban > > >
