(define (make-wrapper-comparator type-test unwrap contents-comparator)
  (make-comparator
   type-test
   (lambda (a b)
     ((comparator-equality-predicate contents-comparator)
      (unwrap a)
      (unwrap b)))
   (if (comparator-ordering-predicate contents-comparator)
       (lambda (a b)
         ((comparator-ordering-predicate contents-comparator)
          (unwrap a)
          (unwrap b)))
       #f)
  (if (comparator-hash-function contents-comparator)
      (lambda (x)
        ((comparator-hash-function contents-comparator) x))
      #f)))

(define (make-composed-comparator type-test . comparators)
  (make-comparator
   type-test
   (if (every comparator-equality-predicate comparators)
       (lambda (a b)
         (generator-every (lambda (cmp)
                            ((comparator-equality-predicate cmp) a b))
                          (list->generator comparators)))
       #f)
   (if (every comparator-ordering-predicate comparators)
       (lambda (a b)
         (let ((gen (list->generator comparators)))
           (let loop ((cmp (gen)))
             (cond ((eof-object? cmp) #f)
                   (((comparator-ordering-predicate cmp) a b) #t)
                   (((comparator-equality-predicate cmp) a b) (loop (gen)))
                   (else #f)))))
       #f)
   (if (every comparator-hash-function comparators)
       (lambda (x)
         (generator-fold bitwise-xor
                         0
                         (gmap (lambda (cmp)
                                 ((comparator-hash-function cmp) x))
                               (list->generator comparators))))
       #f)))

(define-syntax compose-comparator
  (syntax-rules ()
    ((_ type-test (unwrap . more) ...)
     (make-composed-comparator
      type-test
      (let ((cmp ((lambda x
                    (if (null? x) (make-default-comparator)
                        (car x))) . more)))
        (make-wrapper-comparator
         (comparator-type-test-predicate cmp)
         unwrap
         cmp)) ...))))