# HH\Lib\Keyset\intersect

Requires the Hack Standard Library to be installed.

This function is available as Keyset\intersect() in Facebook's www repository.

Returns a new keyset containing only the elements of the first Traversable that appear in all the other ones

namespace HH\Lib\Keyset;

function intersect<Tv as arraykey>(
Traversable<Tv> $first, Traversable<Tv>$second,
Container<Tv> ...$rest, ): keyset<Tv>;  Time complexity: O(n + m), where n is size of $first and m is the combined size of $second plus all the ...$rest Space complexity: O(n), where n is size of \$first

## Returns

• keyset<Tv>