; Problem Set 9 Answers

(include-book "irun")

(in-package "M5")

; Problem 9-1.

; The following constant (which contains a blank to be filled in) defines a
; class named "Cons" with two fields, "car" and "cdr", and one method, named
; "main" which takes no arguments.  Fill in the :code component of the "main"
; method so that executing the main method constructs a linked list
; representing the (1 2 3 . -1).  That is, the topmost Object is a "Cons" with 1
; in the "car" and a reference to an Object representing (2 3 . -1) in the
; "cdr".  The last "Cons" contains a -1 in the "cdr".  You may not store any
; locals.  At the conclusion of your program, the stack should contain exactly
; one item, a reference to the "Cons" in question.

(defconst *ps9-ct*
  (make-ct
   (list (make class
               :name "Cons"
               :supers '("Object")
               :fields '("car" "cdr")
               :methods (list
                         (make method
                               :name "main"
                               :formals nil
                               :sync nil
                               :code
; Answer:                               
                               '((new "Cons")
                                 (dup)
                                 (const 1)
                                 (putfield ("Cons" "car"))
                                 (dup)
                                 (new "Cons")
                                 (dup)
                                 (const 2)
                                 (putfield ("Cons" "car"))
                                 (dup)
                                 (new "Cons")
                                 (dup)
                                 (const 3)
                                 (putfield ("Cons" "car"))
                                 (dup)
                                 (const -1)
                                 (putfield ("Cons" "cdr"))
                                 (putfield ("Cons" "cdr"))
                                 (putfield ("Cons" "cdr"))
                                 (halt))
                                        
                                        ))))))

; The following is a call of irun that should allow you to step through your
; program starting at the 0th instruction in it.

(irun (make state
            :tt
            (list (make thread
                        :id 0
                        :cs
                        (push (make frame
                                    :pc 0
                                    :locs nil
                                    :stk nil
                                    :mloc
                                    '("Cons" "main" 0))
                              nil)
                        :stat 'active
                        :ref nil))
            :hp nil
            :ct *ps9-ct*))

#|

Here is an irun session that shows the program running to
completion:

M5 !>(irun (make state
            :tt
            (list (make thread
                        :id 0
                        :cs
                        (push (make frame
                                    :pc 0
                                    :locs nil
                                    :stk nil
                                    :mloc
                                    '("Cons" "main" 0))
                              nil)
                        :stat 'active
                        :ref nil))
            :hp nil
            :ct *ps9-ct*))

Welcome to irun.  Type :help for help.
-----------------------------------------------------------------
Scene 0
Current thread = (cid 0) = 0
Current state  = (s   0) = 
(MODIFY 0 (S PROTO)
        :PC 0
        :LOCS NIL
        :STK NIL
        :NEXT-INST '(NEW "Cons")
        :MLOC '("Cons" "main" 0))


cmd: :ret

Note:  The state below is stuck!  :Ret did not get back to the caller's
frame!
-----------------------------------------------------------------
Scene 1
Current thread = (cid 1) = 0
Current state  = (s   1) = 
(MODIFY 0 (S 0)
        :PC 19
        :STK '((REF 0))
        :NEXT-INST '(HALT)
        :HP '(((REF 0)
               (("Cons" (("car" 1) ("cdr" (REF 1))))
                ("Object" (("monitor" 0)
                           ("mcount" 0)
                           ("wait-set" 0)))))
              ((REF 1)
               (("Cons" (("car" 2) ("cdr" (REF 2))))
                ("Object" (("monitor" 0)
                           ("mcount" 0)
                           ("wait-set" 0)))))
              ((REF 2)
               (("Cons" (("car" 3) ("cdr" -1)))
                ("Object" (("monitor" 0)
                           ("mcount" 0)
                           ("wait-set" 0)))))))


cmd: :show-sched
(REPEAT 0 20)
cmd: :q
To re-enter this scene, type (irun).

M5 !>

|#