(define (eval exp env)
(cond ((self-evaluationg? exp) exp)
((variable? exp) (lookup-variable-value exp env))
((quoted? exp) (text-of-quotation exp))
((assignment? exp) (eval-assignment exp env))
((call? exp)
(apply (eval (operator exp) env)
(list-of-values (operands 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))))
(define (call? exp)
(tagged-list? exp 'call))
