x-lisp 之所以可以用，就在于可以用 define-data 来描述 ADT：

(define-data (my-list? E)
  nil
  (li (head E) (tail (my-list? E))))

之前在解释器中，是设置新的 value 类型， 在运行时处理这些 value 的 apply：

export type AboutData =
  | DataPredicate
  | DataConstructor
  | DataConstructorPredicate
  | DataAccessor
  | DataModifier

用编译器时，最简单的方案是把这些编译为函数：

;; DataConstructor

(define nil #nil)
(define (li head tail) [#li head tail])

;; DataConstructorPredicate

(define (nil? value) (equal? value #nil))
(define (li? value)
  (and (list? value)
       (equal? (list-length value) 3)
       (equal? (list-head value) #li)))

;; DataAccessor

(define (li-head target) (list-get 1 target))
(define (li-tail target) (list-get 2 target))

;; DataModifier

(define (li-put-head! value target) (list-put! 1 value target))
(define (li-put-tail! value target) (list-put! 2 value target))

(define (li-put-head value target) (list-put 1 value target))
(define (li-put-tail value target) (list-put 2 value target))

;; DataPredicate

(define (my-list? E value)
  (or (nil? value)
      (and (li? value)
           (the E (li-head value))
           (the (my-list? E) (li-tail value)))))