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# formUnion(_:)

Adds the elements of the given set to the set.

```
mutating func formUnion(_ other: Self)
```

## Parameters

`other`

A set of the same type as the current set.

## Discussion

In the following example, the elements of the `visitors` set are added to
the `attendees` set:

```
var attendees: Set = ["Alicia", "Bethany", "Diana"]
let visitors: Set = ["Diana", "Marcia", "Nathaniel"]
attendees.formUnion(visitors)
print(attendees)
// Prints "["Diana", "Nathaniel", "Bethany", "Alicia", "Marcia"]"
```

If the set already contains one or more elements that are also in
`other`, the existing members are kept.

```
var initialIndices = Set(0..<5)
initialIndices.formUnion([2, 3, 6, 7])
print(initialIndices)
// Prints "[2, 4, 6, 7, 0, 1, 3]"
```

---

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