Unwrapping datatypes in Haskell without extraneous code

Question

Say I have

x = Just 2

Is there a way (preferrably a builtin mechanism/function) to use x in a single statement such that if it is a Just, t

Answer 1

For this particular case, fromJust. In general

let Just k = x in f k + 2 == 4

This trick works with any datatype constructor and is very commonly used with (:) for nonempty lists.