[squeak-dev] The Inbox: Collections-ct.947.mcz

Levente Uzonyi leves at caesar.elte.hu
Sat Jun 12 19:52:27 UTC 2021

On Thu, 10 Jun 2021, christoph.thiede at student.hpi.uni-potsdam.de wrote:

> Hi Levente,
>> #sort: and #sorted: expect an argument which responds to #value:value: with a boolean, so both of those examples work if you don't send #asCompareSortFunction to the block.
>> However, #asCompareSortFunction may be useful if you want to create chained sort functions. I'm not sure about the name though.
> Ouch! I did not see the wood for the trees. :-) But yes, if you would like to, for example, invert the order of a compare sort block, the protocols would not match ... So I guess this would still be relevant.

It's not clear to me what you mean by "invert the order of a compare sort 
However, I see one problem with the implementation. It evaluates the block 
but lies about equality. It only returns -1 or 1, never 0. Which means, 
chaining is impossible.
Here's an example:

#((1 a) (1 b)) sorted: [ :a | a first ] ascending, [ :a | a second ] descending
"==>  #(#(1 #b) #(1 #a)) which is fine"


#((1 a) (1 b)) sorted: [ :a :b | a first <= b first ] asCompareSortFunction, [ :a | a second ] descending.
"==>  #(#(1 #a) #(1 #b)) which is not what I would expect"


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