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|
;;; 6.945 Problem Set #8 Source Code
;;; 04/19/2009
;;; Bryan Newbold <bnewbold@mit.edu>
(load "load")
;;;------------------------------------------------------------------------
;;; Problem 8.2B:
(define the-empty-stream (stream))
(define (lazy-fringe subtree)
(define (lazy-walk subtree ans)
(cond ((pair? subtree)
(lazy-walk (car subtree)
(lazy-walk (cdr subtree) ans)))
((null? subtree) ans)
(else (cons-stream subtree ans))))
(lazy-walk subtree the-empty-stream))
(define (lazy-same-fringe? tree1 tree2)
(let lp ((f1 (lazy-fringe tree1))
(f2 (lazy-fringe tree2)))
(cond ((and (stream-null? f1) (stream-null? f2)) #t)
((or (stream-null? f1) (stream-null? f2)) #f)
((eq? (stream-car f1) (stream-car f2))
(lp (stream-cdr f1) (stream-cdr f2)))
(else #f))))
#| Test it!
(lazy-same-fringe?
'((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (f (g (h)))))
;Value: #t
(lazy-same-fringe?
'((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (g (f (h)))))
;Value: #f
|#
;;;------------------------------------------------------------------------
;;; Problem 8.5:
(define (make-pipe)
(let ((queue (queue:make))
(lock (conspire:make-lock)))
(list lock queue)))
(define (pipe-writer p)
(lambda (thing)
(conspire:acquire-lock (car p))
(queue:add-to-end! (cadr p) thing)
(conspire:unlock (car p))))
(define (pipe-reader p)
(lambda ()
(let lp ((nothing-here 0))
(conspire:acquire-lock (car p))
(cond ((queue:empty? (cadr p))
(conspire:unlock (car p))
(conspire:thread-yield)
(lp 0))
(else
(let ((ans (queue:get-first (cadr p))))
(conspire:unlock (car p))
ans))))))
#| Test!
(with-conspiracy
(lambda ()
(define test-pipe (make-pipe))
(define reader (pipe-reader test-pipe))
(define writer (pipe-writer test-pipe))
(writer 10)
(writer 20)
(reader)))
;Value: 10
|#
(define *done* (list '*done*))
(define (piped-same-fringe? tree1 tree2)
(let ((p1 (make-pipe)) (p2 (make-pipe)))
(let ((thread1
(conspire:make-thread
conspire:runnable
(lambda ()
(piped-fringe-generator tree1 (pipe-writer p1)))))
(thread2
(conspire:make-thread
conspire:runnable
(lambda ()
(piped-fringe-generator tree2 (pipe-writer p2)))))
(f1 (pipe-reader p1))
(f2 (pipe-reader p2)))
(let lp ((x1 (f1)) (x2 (f2)))
(cond ((and (eq? x1 *done*) (eq? x2 *done*)) #t)
((or (eq? x1 *done*) (eq? x2 *done*)) #f)
((eq? x1 x2) (lp (f1) (f2)))
(else #f))))))
(define (piped-fringe-generator tree return)
(define (lp tree)
(cond ((pair? tree)
(lp (car tree))
(lp (cdr tree)))
((null? tree) unspecific)
(else
(return tree))))
(lp tree)
(return *done*))
#| Test some more!
(with-conspiracy
(lambda ()
(piped-same-fringe? '((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (f (g (h)))))))
;Value: #t
(with-conspiracy
(lambda ()
(piped-same-fringe? '((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (g (g (h)))))))
;Value: #f
|#
;;;------------------------------------------------------------------------
;;; Problem 8.6:
(define (make-threaded-filter thunker)
(let ((pipe (make-pipe)))
(conspire:make-thread
conspire:runnable
(thunker (pipe-writer pipe)))
(pipe-reader pipe)))
#| Testy!
(with-conspiracy
(lambda ()
(make-threaded-filter (lambda x x))))
;Value: #[compound-procedure 31]
(with-conspiracy
(lambda ()
(define make-an-int
(let ((count 0))
(lambda ()
(set! count (+ count 1))
count)))
(define (return-an-int return)
(return (make-an-int)))
(return-an-int pp)
(define go
(make-threaded-filter return-an-int))
(go)))
;Value: 2
|#
(define *done* (list '*done*))
(define (tf-piped-same-fringe? tree1 tree2)
(let ((f1 (make-threaded-filter (tf-piped-fringe-generator tree1)))
(f2 (make-threaded-filter (tf-piped-fringe-generator tree2))))
(let lp ((x1 (f1)) (x2 (f2)))
(cond ((and (eq? x1 *done*) (eq? x2 *done*)) #t)
((or (eq? x1 *done*) (eq? x2 *done*)) #f)
((eq? x1 x2) (lp (f1) (f2)))
(else #f)))))
(define (tf-piped-fringe-generator tree)
(lambda (return)
(define (lp tree)
(cond ((pair? tree)
(lp (car tree))
(lp (cdr tree)))
((null? tree) unspecific)
(else
(return tree))))
(lp tree)
(return *done*)))
#|
(with-time-sharing-conspiracy
(lambda ()
(tf-piped-same-fringe?
'((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (f (g (h)))))
))
;Value: #t
(with-time-sharing-conspiracy
(lambda ()
(tf-piped-same-fringe?
'((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (g (f (h)))))
))
;Value: #f
(with-time-sharing-conspiracy
(lambda ()
(tf-piped-same-fringe?
'((a b) c ((d)) e (f ((g h))))
'(a b c ((d) () e) (g (f ))))
))
;Value: #f
|#
|
