On Wed, 26 Nov 2014, David T. Lewis wrote:

> On Wed, Nov 26, 2014 at 08:01:49PM +0100, Levente Uzonyi wrote:
>> On Wed, 26 Nov 2014, Eliot Miranda wrote:
>>
>>> Hi All,
>>> ? ? IdentitySet>>collect: answers a Set, not an IdentitySet.? Anyone else
>>> agree this is a serious bug?? Anyone else disagree?
>>>
>>> WTF??
>>>
>>> (IdentitySet withAll: #(1 2 3 1.0 2.0 3.0)) collect: [:e| e] a Set(1.0 2 3)
>>> --
>>> best,Eliot
>>>
>>
>> Sometimes it's feasable to return an IdentitySet, other times it's not, so
>> there's no optimal solution - #collect: can't cover all cases.
>>
>> Set >> #collect: explicitly returns a Set, because this is the least bad
>> solution to handle all of its subclasses reasonably well.
>> In case of WeakSet, returning a WeakSet makes no sense, because some of
>> your objects will disappear immediately.
>> In case of IdentitySet, PluggableSet, KeyedSet and KeyedIdentitySet the
>> returned values may not behave well in the original collection.
>>
>> The best is to always be explicit:
>>
>> (IdentitySet withAll: #(1 2 3 1.0 2.0 3.0)) collect: [ :e | e ] as:
>> IdentitySet
>> "==> an IdentitySet(1 2 3 1.0 2.0 3.0)"
>>
>> Levente
>>
>
> In Squeak 2.8 (checked on http://bertfreudenberg.github.io/SqueakJS/run/):
>
>  (IdentitySet withAll: #(1 2 3 1.0 2.0 3.0)) collect: [:e| e] ==> a Set(2.0 1 2 3 3.0 1.0)
>
>
> But in trunk I get this:
>
>  (IdentitySet withAll: #(1 2 3 1.0 2.0 3.0)) collect: [:e| e] ==> a Set(1 2 3)
>
>
> So answering a Set makes sense for the reasons that Levente explains, but trunk
> is definitely broken WRT the contents of that set.
>
> This bug needs a unit test to go along with whatever fix we agree on.

It's not a bug either. The Floats are not there, because they are equal to 
the integers:

1 = 1.0 "==> true"
1.0 = 1 "==> true"

Therefore they have the same hash:

1 hash "==> 1"
1.0 hash "==> 1"

The bug was in Squeak 2.8:
1.0 = 1 "==> true"
1 = 1.0 "==> true"
1 hash "==> 1"
1.0 hash "==> 61440"

Here's the comment of Float >> hash from The Trunk:
 	"Hash is reimplemented because = is implemented. Both words of the 
float are used. (The bitShift:'s ensure that the intermediate results do 
not become a large integer.) Care is taken to answer same hash as an equal 
Integer."

Levente

>
> Dave
>
>
>