Provides a type for natural numbers.

- data Natural

# Documentation

The type of natural numbers.

Note that matching a natural number against a negative pattern might not work as you expect.
For example, evaluating the following expression results in a run-time error, instead of the
result `"plus five"`

:

case 5 :: Natural of -5 -> "minus five" 5 -> "plus five"

The reason is that the `==`

operator of `Natural`

is used for checking if the patterns
match, making it necessary to convert `-5`

to Natural.