:: x -> (x, x) package:optics-core

Attempt to extract the left-most element from a container, and a version of the container without that element.

>>> uncons []
Nothing

>>> uncons [1, 2, 3]
Just (1,[2,3])

Attempt to extract the right-most element from a container, and a version of the container without that element.

>>> unsnoc "hello!"
Just ("hello",'!')

>>> unsnoc ""
Nothing