[squeak-dev] #species vs OrderedColleciton

Levente Uzonyi leves at caesar.elte.hu
Sun Dec 25 16:09:41 UTC 2016

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 


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?


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

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