Test cases for 1-partial intersections of multisets

[Smoren]

Set::intersectionPartial() test cases added for multisets with $minIntersectionCount = 1.

Explanation of the behavior:

• N — size of initial collections;
• M — min intersection count.

For any N when M = 1 we have a union of sets or multisets.

Some examples of multiset unions from this article:

• [1, 2] ∪ [1] = [1, 2];
• [1, 2] ∪ [1, 1] = [1, 1, 2];
• [1, 1] ∪ [1, 1, 1, 2] = [1, 1, 1, 2].

I've added test cases for this examples and some more complicated cases. They all work predictably.

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[markrogoyski]

Thanks for the explanation and examples. From what I understand, a union of a multiset is really taking the item from the set that has the max cardinality, rather than "adding" them all together. Your examples show the same thing. Thanks.

[Smoren]

OK. I'm glad that we have come to a common perception of this functionality.

You can merge this PR if you want to add the tests included in it.

[Smoren]

BTW, I was very surprised that the concept of partial intersection was not defined in math. I consulted with mathematician friends and decided to write an article on this topic.

Thank you for the inspiration!

[Smoren]

Hi @markrogoyski,

FYI: I've created a new repository with explanation and examples of the partial intersection.