[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
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?
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
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