[Newbies] Re: Another extension proposal -> subsets

[nicolas cellier]

You have one messsage #combinations:atATimeDo: to enumerate partitions, 
but in SequenceableCollection, not in Set:

| collec subset |
collec := 1 to: 4.
subset := OrderedCollection new: (2 raisedTo: collec size).
subset add: #().
1 to: collec size do: [:subSize |
  collec combinations: subSize atATimeDo: [:subArray | subset add: 
subArray copy]].
subset

Mind the copy, because the iteration recycle same subArray for economy.

cdrick a écrit :
>> Set>>subsets
>>  | subsets |
>>  subsets := Set with: self.
>>  self asArray permutationsDo: [:e | subsets add: e asSet].
>>  self do: [:e | subsets addAll: (self copyWithout: e) subsets].
>>  ^ subsets
> 
> nice too and frustrating how you got it quick :)
> 
> I tried a recursive method too first but found the byte ressemblance so...
> My only consolation is that the recursive solution (subsets2) is
> slower and hardly work for Set with more than 10 elements.
> 
> set := #(1 2 3 4 5) asSet.
> [ set subsets  ] timeToRun ." 1"
> [ set subsets2  ] timeToRun. " 8"
> 
> set := #(1 2 3 4 5 6 7) asSet.
> [ set subsets  ] timeToRun ." 5"
> [ set subsets2  ] timeToRun. " 233"
> 
> set := #(1 2 3 4 5 6 7 8 ) asSet.
> [ set subsets  ] timeToRun . " 11"
> [ set subsets2  ] timeToRun. " 1683"
> 
> set := (1 to: 10) asSet.
> [ set subsets  ] timeToRun . " 46"
> 
> set := (1 to: 15) asSet.
> [ set subsets  ] timeToRun ." 2484"
> 
> set := (1 to: 20) asSet.
> [ set subsets  ] timeToRun .  "559953"  "but here the result has (2
> raisedTo: 20)  1 048 576 Sets :)"
> 
> set := (1 to: 50) asSet.
> [ set subsets  ] timeToRun .    "I got a "space is low   wow" :)
> 
> I have to go,
> That was fun :)
> 
> See you
> 
> Cédrick
> 
> 
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