eval.scm

(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))
        ((let? exp) (eval (let->combination exp) env))
        ((let*? exp) (eval (let*->nested-lets exp) env))
        ((letrec? exp) (eval (letrec->let exp) env)) ;;letrecを追加
        ((begin? exp)
         (eval-sequence (begin-actions exp) env))
        ((cond? exp) (eval (cond->if exp) env))
        ((and? exp) (eval (and->if exp) env))
        ((or? exp) (eval (or->if exp) env))
        ((application? exp)
         (my-apply (eval (operator exp) env)
                   (list-of-values (operands exp) env)))
        (else
         (error "Unknown expression type --EVAL" exp))))