; a) Louis's evaluator will incorrectly treat other expressions such as
; (define x 3) as procedure applications because they are represented as lists
; starting too (ie: pair? returns true).

;b )

(load "evaluator.txt")

(define (application? exp) (tagged-list? exp 'call))
(define (operator exp) (cadr exp))
(define (operands exp) (cddr exp))


(define (eval exp env)
  (cond ((self-evaluating? exp) exp)
        ((variable? exp) (lookup-variable-value exp env))
        ((quoted? exp) (text-of-quotation exp))
        ; Move application earlier in the list of cases
        ((application? exp)
         (apply (eval (operator exp) env)
                (list-of-values (operands exp) env)))
        ((assignment? exp) (eval-assignment exp env))
        ((definition? exp) (eval-definition exp env))
        ((if? exp) (eval-if exp env))
        ((lambda? exp)
         (make-procedure (lambda-parameters exp)
                         (lambda-body exp)
                         env))
        ((begin? exp) 
         (eval-sequence (begin-actions exp) env))
        ((cond? exp) (eval (cond->if exp) env))
        (else
         (error "Unknown expression type -- EVAL" exp))))

; 1 ]=> (define the-global-environment (setup-environment))
; 
; ;Value: the-global-environment
; 
; 1 ]=> (driver-loop)
; 
; 
; ;;; M-Eval input:
; (call + 1 2)
; 
; ;;; M-Eval value:
; 3
; 
; ;;; M-Eval input:
; (define (append x y)
;   (if (call null? x)
;       y
;       (call cons (call car x)
;             (call append (call cdr x) y))))
; 
; ;;; M-Eval value:
; ok
; 
; ;;; M-Eval input:
; (call append '(a b c) '(d e f))
; 
; ;;; M-Eval value:
; (a b c d e f)