Ocaml programming please! don't use list module!

rotate shift lst

• Type: int -> 'a list -> 'a list
• Description: Move every element over in lst to the left by the given shift (looping around).
• Assumptions: shift is non-negative.
• Important Note: None of the public or semipublic tests check whether this function works. Write your own tests to verify that your behavior is what you would expect!
• Examples:

  rotate 0 ["a"; "b"; "c"; "d"] = ["a"; "b"; "c"; "d"] rotate 1 ["a"; "b"; "c"; "d"] = ["b"; "c"; "d"; "a"] rotate 2 ["a"; "b"; "c"; "d"] = ["c"; "d"; "a"; "b"] rotate 3 ["a"; "b"; "c"; "d"] = ["d"; "a"; "b"; "c"] rotate 4 ["a"; "b"; "c"; "d"] = ["a"; "b"; "c"; "d"] rotate 5 ["a"; "b"; "c"; "d"] = ["b"; "c"; "d"; "a"]