[squeak-dev] #species vs OrderedColleciton

Tobias Pape Das.Linux at gmx.de
Tue Dec 27 16:52:53 UTC 2016

On 27.12.2016, at 17:45, Levente Uzonyi <leves at caesar.elte.hu> wrote:

> On Tue, 27 Dec 2016, Tobias Pape wrote:
>> On 25.12.2016, at 17:09, Levente Uzonyi <leves at caesar.elte.hu> wrote:
>>> Hi All,
>>> We had a discussion[1] about #species, in the context of Sets and IdentitySets, and its multiple roles which it cannot fulfill[2].
>>> A similar issue arises in case of OrderedCollection and its subclasses, but with a smoother resolution, because an OrderedCollection is always an acceptable result (for #collect:).
>>> So, I suggest we should change OrderedCollection >> #collect: to always return an OrderedCollection. This change obviously would not affect OrderedCollection, but we already have the same override in SortedCollection.
>>> Example:
>>> Currently the following raises and error:
>>> 	(FloatCollection withAll: #(1 2 3)) collect: #asString
>>> Of course, #collect:as: works as expected:
>>> 	(FloatCollection withAll: #(1 2 3)) collect: #asString as: OrderedCollection
>>> 	"==> an OrderedCollection('1.0' '2.0' '3.0')"
>>> So, why not make #collect: behave the same way?
>>> This change would make #species not being used in #collect:, which is similar to the solution we have in Set and subclasses.
>>> Currently #select: and #copyEmpty also use #species, but no class implements #species in the hierarchy. So, changing #species to return OrderedCollection would have unwanted side effects. (This also shows that #species doesn't solve anything here.)
>>> Any objections?
>> Just a question for clarification, would
>> 	(FloatCollection withAll: #(1.0 2.0 3.0)) collect: [:ea | ea sqrt]
>> result in a FloatCollection or in an OrderedCollection?
> An OrderedCollection of course. #collect: would always return an OrderedCollection.

Ok, so to make good use of FloatCollections in the first place i would have to always use 
collect:as: to _stay within_ the class? I somehow do not like that :(. I'd rather have to stay
as much as possible with the closure property for large parts of the collection API.

Whats wrong with species -> class, and collect: staying within the class?
We got several specialized collections, I don't want a buch of collectFloat: collectInteger: collectShortPoint: 
for each and every class. 

Best regards

> Levente
>> Best regards
>> 	-Tobias
>>> Levente
>>> [1] http://lists.squeakfoundation.org/pipermail/squeak-dev/2014-November/180766.html
>>> [2] http://lists.squeakfoundation.org/pipermail/squeak-dev/2014-November/180809.html

More information about the Squeak-dev mailing list