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intersection 

        # Set.intersection

(from ruby core)
---
    intersection(enum)

---

(This method is an alias for Set#&.)

Returns a new set containing elements common to the set and the
given enumerable object.
    Set[1, 3, 5] & Set[3, 2, 1]             #=> #<Set: {3, 1}>
    Set['a', 'b', 'z'] & ['a', 'b', 'c']    #=> #<Set: {"a", "b"}>

This is MURDOC! A Ruby documentation browser inspired by Smalltalk-80. It allows you to learn about Ruby by browsing through its class hierarchies, and see any of its methods.