On 23-05-19 21:18, Nikita Popov wrote: > On Thu, May 23, 2019 at 9:02 PM Dik Takken <d.tak...@xs4all.nl> 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: >> >> array_intersect(...$arrays) >> >> 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.) > > Nikita >
You are completely right, thanks for pointing that out. Regards, Dik Takken -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
