Intersection of two sets or of two lists

The intersect operator is an infixed operator that finds the intersection of the elements of two sets or lists; the result will always be a set.

set[1,2,3,4] intersect set[5,6,3,4]

or:

[1,2,3,4] intersect [5,6,3,4]

⟦ 3,4 ⟧