In the Data.list is set:

---

**"Set" operations**

```
nub :: Eq a => [a] -> [a]

```

*O(n^2). The nub function removes duplicate elements from a list. In particular, it keeps only the first occurrence of each element. (The name nub means `essence'.) It is a special case of nubBy, which allows the programmer to supply their own equality test.*

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I can't use this function directly. How do I use the function nub? Do I have to import something?