> On Thu, May 23, 2019 at 9:02 PM Dik Takken email@example.com> wrote:
>> For array_intersect(), I was actually considering to allow zero
>> arguments. The use case I have in mind is to determine the common
>> elements in a set of zero or more arrays, like this:
>> If that would just return an empty array when $arrays is empty, no
>> additional empty check is needed and the above would do what I
>> intuitively expect it to do.
> Common intuition, but not mathematically sound. Assuming we're intersecting
> subsets of a certain universe U, then the intersection of no sets is U
> itself, not the empty set. (A useful intuition is that intersecting
> additional sets can only make the result smaller -- as such intersecting no
> sets at all yields the largest possible result.)
You are completely right, thanks for pointing that out.