SICP 习题2.22 square迭代式写法的失败

代码产生的结果是

((((()1)2)3)4)

而我们需要的是

(1(2(3(4))))

(define (square-list items)  (define (iter things answer)    (if (null? things)      answer      (iter (cdr things)        (cons answer           (square (car things))))))  (iter items ()))(define square  (lambda (x) (* x x)))(square-list '(1 2 3 4))