提交了很多次才被接受,最后发现居然是 zoj 的 scheme 解释器不支持中括弧语法
(define (sum-of-two-integers)
(let ((a (read))
(b (read)))
(if (or (eof-object? a) (eof-object? b))
(exit 0)
(display (+ a b))))
(newline)
(sum-of-two-integers))
(sum-of-two-integers)