[Cuis-dev] Some more Bag tweaks

[Juan Vuletich]

Well, given that there is no actual guarantee of the iteration order, 
there is no guarantee of the distribution of the picks.

I know it is not likely, but we can't prove it is impossible that this 
strategy answers always the same element. All we need is extremely bad 
luck so the collections are rehashed following the RNG! In practice, 
what is possible, is that the distribution is not exactly uniform.

Another problem is with reproducibility of the results. In tests, or any 
other situation where you need to guarantee the same results, it is 
usually enough to use the same seeds for the RNGs. In these cases, 
results would not be reproducible, because there is no guarantee of 
sequencing between successive runs. Especially if the image is 
restarted, or the data is recreated, in a different image.

What I'd assume is that the user knows what they are doing. Maybe a 
warning in a comment in those methods is in order.

Thanks,

On 5/13/2022 7:11 PM, Luciano Notarfrancesco via Cuis-dev wrote:
> What do you mean by good random properties? It should be uniformly 
> distributed. Do you see any problem in Collection>>#atRandom: or 
> Bag>>#atRandom:?
>
> Thanks!
> Luciano
>
> On Sat, 14 May 2022 at 4:57 AM Juan Vuletich <JuanVuletich at zoho.com 
> <mailto:JuanVuletich at zoho.com>> wrote:
>
>     Anyone using #atRandom: on a non-sequenceable collection should be
>     aware that no good random properties can be guaranteed, right?
>
>     Anyway, just pushed to GitHub.
>
>     Thanks,
>
>
>     On 5/9/2022 7:56 AM, Luciano Notarfrancesco via Cuis-dev wrote:
>>     Juan, please don't forget to look at the changeset in my previous
>>     mail when you have time.
>>
>>     Here are some additional tweaks. I reimplemented
>>     Collection>>#identityIncludes: using #allSatisfy: instead of
>>     #do:, in this way it is fast for Bags too, and it mirrors the
>>     implementation of Collection>>#includes:.
>>
>>     I also implemented a fast Bag>>#atRandom:, and implemented a
>>     general Collection>>#atRandom:. Originally #atRandom: was not
>>     implemented in Collection, so I implemented a generic version
>>     that only assumes the collection understands #size and #do:.
>>
>>     Thanks,
>>     Luciano
>>
>>     On Tue, May 3, 2022 at 7:54 AM Luciano Notarfrancesco
>>     <luchiano at gmail.com <mailto:luchiano at gmail.com>> wrote:
>>
>>         Here are some more methods that take advantage of the
>>         structure of a Bag (#allSatisfy:, #anySatisfy:, #max:, #min:,
>>         #sum:, etc).
>>
>>         Also made some tweaks to some methods in Collection to call
>>         existing methods instead of reimplementing, in order to
>>         simplify the changes in Bag (otherwise. for example, I'd have
>>         to implement #sum, #sum: and #sum:ifEmpty: in Bag instead of
>>         only implementing #sum:ifEmpty). And I changed
>>         Collection>>#product to produce an error when the collection
>>         is empty instead of returning 1 (to be consistent with
>>         Collection>>#sum:).
>>
>>         All base image tests pass, but please review.
>>
>>         Also, while running tests I got a walkback on
>>         BitBltCanvasEngine, see the attached log.
>>
>
>
>     -- 
>     Juan Vuletich
>     www.cuis-smalltalk.org  <http://www.cuis-smalltalk.org>
>     https://github.com/Cuis-Smalltalk/Cuis-Smalltalk-Dev
>     https://github.com/jvuletich
>     https://www.linkedin.com/in/juan-vuletich-75611b3
>     https://independent.academia.edu/JuanVuletich
>     https://www.researchgate.net/profile/Juan-Vuletich
>     https://patents.justia.com/inventor/juan-manuel-vuletich
>     https://twitter.com/JuanVuletich
>


-- 
Juan Vuletich
www.cuis-smalltalk.org
https://github.com/Cuis-Smalltalk/Cuis-Smalltalk-Dev
https://github.com/jvuletich
https://www.linkedin.com/in/juan-vuletich-75611b3
https://independent.academia.edu/JuanVuletich
https://www.researchgate.net/profile/Juan-Vuletich
https://patents.justia.com/inventor/juan-manuel-vuletich
https://twitter.com/JuanVuletich

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