;; ---- c311, Spring 1996
;; ---- Solutions to Assignment 9, parameters and exceptions

(define parameter-while
  (lambda (p v th)
    (let ([pval (p)])
      (p v)
      (let ([endval (th)])
	(p pval)
	endval))))

;; ----

(define raise
  (lambda (v)
    (error 'raise "Unhandled exception: ~s" v)))

(define try/wall
  (lambda (body-thunk guard-proc handler-proc)
    (call/cc
      (lambda (k)
	(fluid-let ([raise (let ([outer-raise raise])
			     (lambda (v)
			       (if (guard-proc v)
				   (fluid-let ([raise outer-raise])
				     (k (handler-proc v)))
				   (outer-raise v))))])
	  (body-thunk))))))