(define-library (list-error)
  (import (scheme base))
  (export make-list-error
          list-error-list
          list-error-tail
          list-error-message
          list-error?
          circular-list-error?
          dotted-list-error?)
  (begin

    (define-record-type <list-error>
      (make-list-error list tail)
      list-error?
      (list list-error-list)
      (tail list-error-tail))

    (define (list-error-message err)
      (let ((tail (list-error-tail obj)))
        (cond ((null? tail)
               "Proper list")
              ((pair? tail)
               "Circular list")
              ((eq? tail (list-error-list obj))
               "Not a list")
              (else
               "Dotted list"))))

    (define (circular-list-error? obj)
      (and (list-error? obj)
           (pair? (list-error-tail obj))))

    (define (dotted-list-error? obj)
      (and (list-error? obj)
           (not (null-or-pair? (list-error-tail obj)))))))