为什么+和*分别评估为0和1？

我正在使用GNU/MIT Scheme:

1 ]=> (+)

;Value: 0

1 ]=> (*)

;Value: 1

1 ]=> (-)

;The procedure #[arity-dispatched-procedure 2] has been called with 0 arguments; it requires at least 1 argument.
;To continue, call RESTART with an option number:
; (RESTART 1) => Return to read-eval-print level 1.

2 error> (/)

;The procedure #[arity-dispatched-procedure 3] has been called with 0 arguments; it requires at least 1 argument.
;To continue, call RESTART with an option number:
; (RESTART 2) => Return to read-eval-print level 2.
; (RESTART 1) => Return to read-eval-print level 1.

怎么会+和*分别都评估,以0和1.为什么要评估-并/抛出错误？

这是Scheme定义的一部分还是GNU/MIT Scheme中的实现细节？