3 (define (make-frame variables values)
4 (if (not (= (length variables)
6 (error "Number of variables and values should be the same -- MAKE-FRAME")
7 (map cons variables values)))
9 (define (frame-variables frame)
12 (define (frame-values frame)
15 (define (add-binding-to-frame! var val frame)
16 (set! frame (cons (cons var val) frame)))