(define-library (cuprate rewriters)
  (import (scheme base))
  (export rewriiters rewrite)
  (begin
    (define (default-on-pair pair)
      (cons (test-rewrite (car pair))
            (test-rewrite (cdr pair))))
    (define (default-on-vector vec)
      (vector-map test-rewrite vec))
    (define (default-on-error error)
      (let ((msg (error-object-message error))
            (irritants (error-object-irritants error)))
        (cons 'error (cons msg irritants))))
    (define rewriters
      (make-parameter `((,pair? . ,default-on-pair)
                        (,vector? . ,default-on-vector)
                        (,error-object? . ,default-on-error))))
    (define (rewrite obj)
      (let loop ((rewriters (rewriters)))
        (cond
          ((null? rewriters) obj)
          (((caar rewriters) obj) ((cdar rewriters) obj))
          (else (loop (cdr rewriters))))))))