Exercise 3.35: Ben Bitdiddle tells Louis that
one way to avoid the trouble in Exercise 3.34 is to define a squarer as a
new primitive constraint.  Fill in the missing portions in Ben’s outline for a
procedure to implement such a constraint:


(define (squarer a b)
  (define (process-new-value)
    (if (has-value? b)
        (if (< (get-value b) 0)
            (error "square less than 0: 
                    SQUARER" 
                   (get-value b))
            ⟨alternative1⟩)
        ⟨alternative2⟩))
  (define (process-forget-value) ⟨body1⟩)
  (define (me request) ⟨body2⟩)
  ⟨rest of definition⟩
  me)