# :: Ord a => [a] -> [a] -package:prelude-compat package:protolude

The sort function implements a stable sorting algorithm. It is a special case of sortBy, which allows the programmer to supply their own comparison function. Elements are arranged from lowest to highest, keeping duplicates in the order they appeared in the input.
```>>> sort [1,6,4,3,2,5]
[1,2,3,4,5,6]
```
reverse xs returns the elements of xs in reverse order. xs must be finite.
```>>> reverse []
[]

>>> reverse [42]
[42]

>>> reverse [2,5,7]
[7,5,2]

>>> reverse [1..]
* Hangs forever *
```
cycle ties a finite list into a circular one, or equivalently, the infinite repetition of the original list. It is the identity on infinite lists.
```>>> cycle []
*** Exception: Prelude.cycle: empty list

>>> take 20 \$ cycle [42]
[42,42,42,42,42,42,42,42,42,42...

>>> take 20 \$ cycle [2, 5, 7]
[2,5,7,2,5,7,2,5,7,2,5,7...
```
Return all the elements of a list except the last one. The list must be non-empty.
```>>> init [1, 2, 3]
[1,2]

>>> init [1]
[]

>>> init []
*** Exception: Prelude.init: empty list
```
Extract the elements after the head of a list, which must be non-empty.
```>>> tail [1, 2, 3]
[2,3]

>>> tail [1]
[]

>>> tail []
*** Exception: Prelude.tail: empty list
```