Let me offer a simple example. #(a a) isSortedBy: [:x :y | (x <= y) not] is false, while #(a a) isSortedBy: [:x :y | y <= x] is true. On 24 April 2018 at 02:43, Erik Stel <erik.stel@gmail.com> wrote:
Richard,
Can you explain me what you mean by "sortBlock is supposed to act like #<="? Isn't it up to the developer to decide what the logic should be? I simply used #<= because #> might not have been implemented for all relevant classes, but would otherwise have chosen #> as a means to get the 'reversal' of #<=.
Your solution is not resulting in the behaviour I would expect it. Adding elements which are compared equally, but still have a different value, do not get added in the same position. In the examples below I use Associations, since it compares on the key only (for #<= comparison).
Consider a regular SortedCollection with default sortBlock (set explicitly): | aCollection | aCollection := SortedCollection sortBlock: [ :a :b | a <= b ]. {#k->'Some'. #k->'Value'. #k->'Or'. #k->'Other'} do: [ :each | aCollection add: each ]. aCollection. "a SortedCollection(#k->'Some' #k->'Value' #k->'Or' #k->'Other')"
When I create a SortedCollection with your code's sortBlock reversed I get: | aCollection | aCollection := SortedCollection sortBlock: [ :a :b | b <= a ]. {#k->'Some'. #k->'Value'. #k->'Or'. #k->'Other'} do: [ :each | aCollection add: each ]. aCollection. "a SortedCollection(#k->'Some' #k->'Value' #k->'Or' #k->'Other')"
The order of the result is the same in both situations. What I would expect is the result you get from the sortBlock I suggested: | aCollection | aCollection := SortedCollection sortBlock: [ :a :b | (a <= b) not ]. {#k->'Some'. #k->'Value'. #k->'Or'. #k->'Other'} do: [ :each | aCollection add: each ]. aCollection. "a SortedCollection(#k->'Other' #k->'Or' #k->'Value' #k->'Some')"
This last result is the reversal of the original result.
(side note) IF in the above #addAll: was used instead of the repeated #add:, things might be different again. Since the #addAll: implementation would on some occasions (when size of receiver vs size of added elements is certain ratio) add the elements at the end and then perform a #reSort. With values being compared as equal, the order will be decided by the order they were added. So the result of #addAll: depends on the collection sizes. This might not be what a user would expect ;-).
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