CS 333  HW 05 — Begin EVAL and friendsDue:  Monday, Feb 18Part two will be the rest of EVAL, due the following Monday.0.  Refresh your memory on • what is a legal form in LISP • what are the rules for evaluation of a form? • what are the important “special” functions?This is not bad practice for the quiz, btw.1.  For this week, we’ll get started on programming our own version of EVAL, which we’ll call 3EVAL.  (By using a different name, we avoid wrecking the underlying LISP mechanism, and also keep from accidentally calling the wrong version of a function)To keep things from getting too complicated in any one function, we’ll break the project into several functions.All of these functions will need a second argument, the “environment” … which is the way we deal with the value of variables.  Don’t worry too much right now, but do provide the extra arg ENV so we don’t have to go back and put it in.  If you’re testing 3EVAL, you can supply NIL.Top function:  3EVAL  args: a LISP form, and an “environment”  action:  evaluate the form and return the result            — remember: the top level of SBCL does a loop:   (PRINT (EVAL (READ))).  We’re all familiar                with seeing EVAL in action, even though we rarely call it directly.  Outline:  if the form is atomic, call 3EVAL-ATOM to do the job.     If not, it must be a list.  If the CAR of the list is atomic, call 3EVAL-ATOM-CAR to do the job     If not, it might be a lambda: don’t worry about that for right now.     Otherwise, print an error message.  Be sure you print the offending form!Helper function:  3EVAL-ATOM  arg:  form (an atom — don’t have to check that, it has to be one), and an environment  action:  determine value and return it.    Outline:  determine which kind of atom we have.  (Number, string, symbol).  The first two are easy, as they’re self-evaluating.  For symbols, we look them up in the ENV — which we’ve been passing along as that second argument to all the…