ian 2

(define apply-env
    (lambda (env search-sym)
      (cases environment env
             (empty-env ()
                        (eopl:error 'apply-env "No binding for ~s" search-sym))
             (extend-env (var val saved-env)
                         (if (eqv? search-sym var)
                             (if (vector? val)
                                 (vector-ref val)
                                 (val))
                             (apply-env saved-env search-sym))))))