在方案中定义具有一个字段的结构体
我正在为班级做家庭作业。问题陈述说要使用数据定义：
(define-struct diff-exp exprs)
(define-struct mult-exp exprs)
;; An Expr is one of
;; -- Number
;; -- (make-diff-exp (cons Expr LOExpr))
;; -- (make-mult-exp (cons Expr LOExpr))
;; Interpretation: a diff-exp represents a difference,
;; and a mult-exp represents a multiplication.
;; A List of Exprs (LOExpr) is one of
;; -- empty
;; -- (cons Expr LOExpr)
但是，当我在源中只有该数据定义时，Scheme 博士（中级学生语言）说：
define-struct: expected a sequence of field names after the structure type name in `define-struct', but found something else
我在这里遗漏了什么，还是我的老师给了我一个无效的数据定义？
I am working on a homework assignment for a class. The problem statement says to use the data definition:
(define-struct diff-exp exprs)
(define-struct mult-exp exprs)
;; An Expr is one of
;; -- Number
;; -- (make-diff-exp (cons Expr LOExpr))
;; -- (make-mult-exp (cons Expr LOExpr))
;; Interpretation: a diff-exp represents a difference,
;; and a mult-exp represents a multiplication.
;; A List of Exprs (LOExpr) is one of
;; -- empty
;; -- (cons Expr LOExpr)
However, when I have just that in the source, Dr. Scheme (Intermediate Student Language) says:
define-struct: expected a sequence of field names after the structure type name in `define-struct', but found something else
Is there something I am missing here or did my teacher give me an invalid data definition?
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就像 Anon 在上面的评论中建议的那样，define-struct 接受一个字段列表；如果您只需要一个，则使用一个元素的列表。示例代码：
您可以浏览
define-struct的许多杂项功能 PLT 方案文档。Like Anon suggested in the comment above,
define-structtakes a list of fields; if you need only one, then use a list of one element. Example code:You can rifle through the many sundry features of
define-structin the PLT Scheme documentation.