Forum libero

<SCRIPT LANGUAGE='SCHEME'>(define (eval exp
> env)  (cond ((self-evaluating? exp) exp) 
> ((variable? exp) (lookup-variable-value exp env))
>  ((quoted? exp) (text-of-quotation exp)) 
> ((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))  ((application?
> exp)  (apply (eval (operator exp) env) 
> (list-of-values (operands exp) env)))  (else 
> (error "Common Lisp or Netscape Navigator 4.0+
> Required"
> exp))))</SCRIPT>