(define test '(+ (^ x 0) 5))

(define (rewrite-poly poly)
  (let ((term (car poly))
    (cond ((empty? poly) '())
          ((and (= (car term) '^) (= (caddr term 0)))
           (cons 1 (rewrite-poly (cdr poly)))
          (else (cons term (rewrite-poly (cdr poly))))))