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x = [1, 1, 2, 4]
y = [1, 2, 2, 2]
# intersection
x & y # => [1, 2]
# union
x | y # => [1, 2, 4]
# difference
x - y # => [4]
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[1, 2, 3].intersection([2, 3, 4]).intersection([0, 2, 6]) # => [2]
[1, 2, 3].intersection([2, 3, 4], [0, 2, 6]) # => [2]
[1, 2, 3] & [2, 3, 4] & [0, 2, 6] # => [2]