Chris Muller wrote in another thread:

> There was another change to earlier today that you may be interested
> in asking that question about too, since it changed 19-year old
> SequenceableCollection>>#= with a one-day old replacement and actually
> went into trunk.

Please note that this has been discussed more than a month ago, and the
discussion clearly converged to this consensus:
- having Interval and Array being = is not an important feature
- it seriously impacts efficiency of Interval hash
- it causes long standing bugs that we carry for years (19 years or so)

What's the point of having Interval = Array, when we have OrderedCollection
~= Array at the same time?
A less arbitrary feature would be a generalization of eachOperand
isSequenceable ==> testThatElementsAreSameSequence:
But it's both too hard to maintain (a bug factory), aand a problem for
efficient implementation of some specialized collection.
At the end, it's maybe not so much a desirable feature and it's practically
not used in trunk images, apart for writing shorter tests.
I'm not a big fan of C motto when used with extremism: you don't pay for
what you don't buy.
But I have the feeling that it makes sense here.

BTW, I don't like  hasEqualElements: because I mentally associate elements
to Set, and for me #(1 2 3)  hasEqualElements: #(3 1 2), just with a
different order.
I would prefer something like isSameSequenceAs: which clearly tells about
the ordering.

Le mer. 13 févr. 2019 à 17:21, Chris Cunningham <cunningham.cb at gmail.com> a
écrit :

> Thank you. This was an angle I hadn't thought of - but definitely opens up
> how to fix it correctly:
> *>Definitively abandon SequenceableCollection equality tests based on
> equal species. *
>
> On Tue, Feb 12, 2019 at 2:56 PM <commits at source.squeak.org> wrote:
>
>> Nicolas Cellier uploaded a new version of Collections to project The
>> Trunk:
>> http://source.squeak.org/trunk/Collections-nice.820.mcz
>>
>> ==================== Summary ====================
>>
>> Name: Collections-nice.820
>> Author: nice
>> Time: 12 February 2019, 11:56:35.262017 pm
>> UUID: bb383133-067c-4133-987b-c481a7de69c7
>> Ancestors: Collections-ul.819, Collections-cbc.813
>>
>> Definitively abandon SequenceableCollection equality tests based on equal
>> species.
>>
>> Old behaviour can still be obtained thru hasEqualElements: but the
>> default is to not try to support such trans-class equality feature because
>> it is much too complex.
>>
>> Particularly Interval are no more equal to Arrays with same sequence. We
>> can thus optimize hash a bit more and fix the old bugs of equa objects with
>> different hashes. Merge Collections-cbc.813 for this and rehashAll in
>> postscript.
>>
>> There are not so many classes concerned by this change, mainly RunArray,
>> Interval and LinkedList:
>>
>> Collection withAllSubclasses select: [:e | [e basicNew species ~= e] on:
>> Error do: [false]]
>> -> an OrderedCollection(WeakRegistry LinkedList Interval ByteCharacterSet
>> CharacterSetComplement LazyCharacterSet WideCharacterSet ShortRunArray
>> Semaphore Mutex TextLineInterval WeakArray Monitor MCVersionName ByteSymbol
>> WideSymbol)
>>
>> We will have to change the tests that rely on such equality.
>>
>> =============== Diff against Collections-ul.819 ===============
>>
>> Item was changed:
>>   ----- Method: FloatArray>>= (in category 'comparing') -----
>>   = aFloatArray
>> -       | length |
>>         <primitive: 'primitiveEqual' module: 'FloatArrayPlugin'>
>> +       ^super = aFloatArray!
>> -       aFloatArray class = self class ifFalse: [^ false].
>> -       length := self size.
>> -       length = aFloatArray size ifFalse: [^ false].
>> -       1 to: self size do: [:i | (self at: i)
>> -                       = (aFloatArray at: i) ifFalse: [^ false]].
>> -       ^ true!
>>
>> Item was changed:
>>   ----- Method: Interval>>= (in category 'comparing') -----
>>   = anObject
>> -
>>         ^ self == anObject
>> +               or: [anObject isInterval
>> +                       ifFalse: [super = anObject]
>> +                       ifTrue:
>> +                               [start = anObject first
>> +                                and: [step = anObject increment
>> +                                and: [self last = anObject last]]]]!
>> -               ifTrue: [true]
>> -               ifFalse: [anObject isInterval
>> -                       ifTrue: [start = anObject first
>> -                               and: [step = anObject increment
>> -                                       and: [self last = anObject last]]]
>> -                       ifFalse: [super = anObject]]!
>>
>> Item was changed:
>>   ----- Method: Interval>>hash (in category 'comparing') -----
>>   hash
>>         "Hash is reimplemented because = is implemented."
>> +         ^((start hash hashMultiply bitXor: self last hash) hashMultiply
>> +                 bitXor: self size)!
>> -
>> -       ^(((start hash bitShift: 2)
>> -               bitOr: stop hash)
>> -               bitShift: 1)
>> -               bitOr: self size!
>>
>> Item was changed:
>>   ----- Method: RunArray>>= (in category 'comparing') -----
>>   = anObject
>> +       self == anObject ifTrue: [^ true].
>> -       "Test if all my elements are equal to those of anObject"
>> -
>>         ^anObject class == self class
>> +               and:
>> -               ifTrue: "Faster test between two RunArrays"
>>                         [(runs hasEqualElements: anObject runs)
>> +                        and: [values hasEqualElements: anObject values]]!
>> -                        and: [values hasEqualElements: anObject values]]
>> -               ifFalse:
>> -                       [anObject isCollection and: [self
>> hasEqualElements: anObject]]!
>>
>> Item was changed:
>>   ----- Method: SequenceableCollection>>= (in category 'comparing') -----
>>   = otherCollection
>>         "Answer true if the receiver is equivalent to the otherCollection.
>> +       First test for identity, then rule out different class and sizes
>> of
>> -       First test for identity, then rule out different species and
>> sizes of
>>         collections. As a last resort, examine each element of the
>> receiver
>>         and the otherCollection."
>>
>>         self == otherCollection ifTrue: [^ true].
>> +       self class == otherCollection class ifFalse: [^ false].
>> -       self species == otherCollection species ifFalse: [^ false].
>>         ^ self hasEqualElements: otherCollection!
>>
>> Item was changed:
>>   ----- Method: Symbol>>= (in category 'comparing') -----
>>   = aSymbol
>>         "Compare the receiver and aSymbol."
>>         self == aSymbol ifTrue: [^ true].
>> +       aSymbol isSymbol ifTrue: [^ false].
>> -       self class == aSymbol class ifTrue: [^ false].
>>         "Use String comparison otherwise"
>>         ^ super = aSymbol!
>>
>> Item was changed:
>> + (PackageInfo named: 'Collections') postscript: 'Character
>> initializeClassificationTable.
>> + HashedCollection rehashAll.'!
>> - (PackageInfo named: 'Collections') postscript: 'Character
>> initializeClassificationTable'!
>>
>>
>>
>
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