Usenet 1994 October/usenetsourcesnewsgroupsinfomagicoctober1994disk2.iso/misc/volume8/elk/part09

Text File | 1989-09-23 | 57.0 KB | 1,675 lines

Newsgroups: comp.sources.misc
From: [e-mail] (Brandon S. Allbery - comp.sources.misc)
Subject: v08i057: Elk (Extension Language Toolkit) part 09 of 14
Reply-To: [e-mail] (Oliver Laumann)

Posting-number: Volume 8, Issue 57
Submitted-by: [e-mail] (Oliver Laumann)
Archive-name: elk/part09

[Let this be a lesson to submitters:  this was submitted as uuencoded,
compressed files.  I lost the source information while unpacking it; this
is the best approximation I could come up with.  ++bsa]

#! /bin/sh
# This is a shell archive.  Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file".  To overwrite existing
# files, type "sh file -c".  You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g..  If this archive is complete, you
# will see the following message at the end:
#        "End of archive 9 (of 14)."
# Contents:  tst/billiard lib/xlib/examples/properties
#   lib/xlib/examples/track lib/xlib/examples/picture
#   lib/xlib/examples/useful lib/xlib/pixel.c
# Wrapped by net@tub on Sun Sep 17 17:32:32 1989
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f tst/billiard -a "${1}" != "-c" ; then
  echo shar: Will not over-write existing file \"tst/billiard\"
else
echo shar: Extracting \"tst/billiard\" \(46118 characters\)
sed "s/^X//" >tst/billiard <<'END_OF_tst/billiard'
X;;;
X;;; BILLIARD.SCM: This file contains code for a very simple billiard ball
X;;;               simulator.  The simulation takes place in two dimensions.
X;;;               The balls are really disks in that their height is not taken
X;;;               into account.  All interactions are assumed to be
X;;;               frictionless so spin in irrelevant and not accounted for.
X;;;               (See section on limitations.)
X;;;
X;;; NOTES: A simulation is initiated by creating a number of balls and bumpers
X;;;        and and specifying a duration for the simulation.  For each ball,
X;;;        its mass, radius, initial position, and initial velocity must be
X;;;        specified.  For each bumper, the location of its two ends must be
X;;;        specified.  (Bumpers are assumed to have zero width.)
X;;;
X;;;        A sample run might be started as follows:
X;;;        (simulate
X;;;         (list (make-ball 2 1 9 5 -1 -1)
X;;;               (make-ball 4 2 2 5 1 -1))
X;;;         (list (make-bumper 0 0 0 10)
X;;;               (make-bumper 0 0 10 0)
X;;;               (make-bumper 0 10 10 10)
X;;;               (make-bumper 10 0 10 10))
X;;;         30)
X;;;
X;;;        It would create one billiard ball of mass 2 and radius 1 at position
X;;;        (9, 5) with initial velocity (-1, -1) and a second ball of mass 4
X;;;        and radius 2 at position (2, 5) with initial velocity (1, -1).  The
X;;;        table would be a 10X10 square.  (See diagram below)
X;;;
X;;;        +---------------------------+
X;;;        |                           |
X;;;        |                           |
X;;;        |    XXXX                   |
X;;;        |  XXXXXXXX             XX  |
X;;;        |XXXXXX4XXXXX         XXX2XX|
X;;;        |  XXXXXXXX            /XX  |
X;;;        |    XXXX \                 |
X;;;        |                           |
X;;;        |                           |
X;;;        +---------------------------+
X;;;
X;;; LIMITATIONS:  This simulator does not handle 3 body problems correctly.  If
X;;;               3 objects interact at one time, only the interactions of 2 of
X;;;               the bodies will be accounted for.  This can lead to strange
X;;;               effects like balls tunneling through walls and other balls.
X;;;               It is also possible to get balls bouncing inside of each
X;;;               other in this way.
X;;;
X
X
X;;MAKE-QUEUE-RECORD returns a queue record with the given next, previous, and
X;;value values
X;;NEXT = The next record pointer
X;;PREV = The previous record pointer
X;;REST = A list of values for any optional fields (this can be used for
X;;       creating structure inheritance)
X(define-macro (make-queue-record next prev . rest)
X  `(vector ,next ,prev ,@rest))
X
X;;QUEUE-RECORD-NEXT returns the next field of the given queue record
X;;QUEUE-RECORD = The queue record whose next field is to be returned
X(define-macro (queue-record-next queue-record)
X  `(vector-ref ,queue-record 0))
X
X;;SET-QUEUE-RECORD-NEXT! sets the next field of the given queue record
X;;QUEUE-RECORD = The queue record whose next field is to be set
X;;VALUE = The value to which the next field is to be set
X(define-macro (set-queue-record-next! queue-record value)
X  `(vector-set! ,queue-record 0 ,value))
X
X;;QUEUE-RECORD-PREV returns the prev field of the given queue record
X;;QUEUE-RECORD = The queue record whose prev field is to be returned
X(define-macro (queue-record-prev queue-record)
X  `(vector-ref ,queue-record 1))
X
X;;SET-QUEUE-RECORD-PREV! sets the prev field of the given queue record
X;;QUEUE-RECORD = The queue record whose prev field is to be set
X;;VALUE = The value to which the prev field is to be set
X(define-macro (set-queue-record-prev! queue-record value)
X  `(vector-set! ,queue-record 1 ,value))
X
X;;QUEUE-RECORD-LEN returns the length of a queue record which has no optional
X;;fields
X(define-macro (queue-record-len) 2)
X
X;;QUEUE-HEAD returns a dummy record at the end of the queue with the record
X;;with the smallest key.
X;;QUEUE = the queue whose head record is to be returned
X(define-macro (queue-head queue)
X  `(vector-ref ,queue 0))
X
X;;QUEUE-TAIL returns a dummy record at the end of the queue with the record
X;;with the largest key.
X;;QUEUE = the queue whose tail record is to be returned
X(define-macro (queue-tail queue)
X  `(vector-ref ,queue 1))
X
X;;QUEUE-<? returns the less-than comparitor to be used in sorting
X;;records into the queue
X;;QUEUE = The queue whose comparitor is to be returned
X(define-macro (queue-<? queue)
X  `(vector-ref ,queue 2))
X
X
X;;MAKE-SORTED-QUEUE returns a queue object.  A queue header is a vector which
X;;contains a head pointer, a tail pointer, and a less-than comparitor.
X;;QUEUE-<? = A predicate for sorting queue items
X(define (make-sorted-queue queue-<?)
X  (let ((queue
X     (vector
X      (make-queue-record        ;The queue head record has no initial
X       '()                ;next, previous, or value values
X       '())
X      (make-queue-record        ;The queue tail record has no intial
X       '()                ;next, previous, or value values
X       '())
X      queue-<?)))
X    (set-queue-record-next!
X     (queue-head queue)
X     (queue-tail queue))
X    (set-queue-record-prev!
X     (queue-tail queue)
X     (queue-head queue))
X    queue))
X
X;;MAKE-EVENT-QUEUE-RECORD returns an event queue record with the given next,
X;;previous, object, and collision-time values
X;;NEXT = The next record pointer
X;;PREV = The previous record pointer
X;;OBJECT = The simulation object associated with this record
X;;COLLISION-TIME = The collision time for this object
X(define-macro (make-event-queue-record next prev object collision-time)
X  `(make-queue-record ,next ,prev ,object ,collision-time))
X
X;;EVENT-QUEUE-RECORD-OBJECT returns the object associated with the given record
X;;QUEUE-RECORD = The queue record whose object field is to be returned
X(define-macro (event-queue-record-object queue-record)
X  `(vector-ref ,queue-record ,(queue-record-len)))
X
X;;EVENT-QUEUE-COLLISION-TIME returns the collision time associated with the
X;;given queue record
X;;QUEUE-RECORD = The queue record whose collision time field is to be returned
X(define-macro (event-queue-record-collision-time queue-record)
X  `(vector-ref ,queue-record ,(1+ (queue-record-len))))
X
X;;SET-EVENT-QUEUE-COLLISION-TIME! sets the collision time associated with the
X;;given queue record
X;;QUEUE-RECORD = The queue record whose collision time field is to be returned
X;;VALUE = The value to which it is to be set
X(define-macro (set-event-queue-record-collision-time! queue-record value)
X  `(vector-set! ,queue-record ,(1+ (queue-record-len)) ,value))
X
X
X;;QUEUE-INSERT inserts the given record in the given queue based on its value
X;;QUEUE = The queue into which the record is to be inserted
X;;QUEUE-RECORD = The record to be inserted in the queue
X(define (queue-insert queue queue-record)
X  (define (actual-insert insert-record next-record)
X    (if (or                ;If the insert position has been found
X     (eq? next-record        ;or the end on the queue has been
X          (queue-tail queue))    ;reached
X     ((queue-<? queue)
X      insert-record
X      next-record))
X    (sequence            ;Link the insert record into the queue
X      (set-queue-record-next!    ;just prior to next-record
X       (queue-record-prev
X        next-record)
X       insert-record)
X      (set-queue-record-prev!
X       insert-record
X       (queue-record-prev
X        next-record))
X      (set-queue-record-next!
X       insert-record
X       next-record)
X      (set-queue-record-prev!
X       next-record
X       insert-record))
X    (actual-insert            ;Else, continue searching for the
X     insert-record            ;insert position
X     (queue-record-next
X      next-record))))
X  (actual-insert            ;Search for the correct position to
X   queue-record                ;perform the insert starting at the
X   (queue-record-next            ;queue head and perform the insert
X    (queue-head queue))))        ;once this position has been found
X
X;;QUEUE-REMOVE removes the given queue record from its queue
X;;QUEUE-RECORD = The record to be removed from the queue
X(define (queue-remove queue-record)
X  (set-queue-record-next!
X   (queue-record-prev
X    queue-record)
X   (queue-record-next
X    queue-record))
X  (set-queue-record-prev!
X   (queue-record-next
X    queue-record)
X   (queue-record-prev
X    queue-record)))
X
X;;QUEUE-SMALLEST returns the queue record with the smallest key on the given
X;;queue
X;;QUEUE = The queue from which the smallest record is to be extracted
X(define (queue-smallest queue)
X  (queue-record-next
X   (queue-head queue)))
X
X
X;;CLEAR-QUEUE! clears the given queue by destructively removing all the records
X;;QUEUE = The queue to be cleared
X(define (clear-queue queue)
X  (set-queue-record-next!
X   (queue-head queue)
X   (queue-tail queue))
X  (set-queue-record-prev!
X   (queue-tail queue)
X   (queue-head queue)))
X
X;;EMPTY-QUEUE? returns true if the given queue is empty
X;;QUEUE = The queue to be tested for emptiness
X(define (empty-queue? queue)
X  (eq? (queue-record-next
X    (queue-head queue))
X       (queue-tail queue)))
X
X
X;;MAKE-SIMULATION-OBJECT returns a simulation object containing the given
X;;fields
X;;COLLISION-PROCEDURE = A function for processing information about a potential
X;;                      collision between this object and some ball
X;;REST = A list of values for any optional fields (this can be used for
X;;       creating structure inheritance)
X(define-macro (make-simulation-object collision-procedure . rest)
X  `(vector ,collision-procedure ,@rest))
X
X;;SIMULATION-OBJECT-COLLLISION-PROCEDURE returns the collision procedure for
X;;the given simulation object
X;;OBJECT = The object whose collision procedure is to be returned
X(define-macro (simulation-object-collision-procedure object)
X  `(vector-ref ,object 0))
X
X;;SIMULATION-OBJECT-LEN returns the length of a simulation object which has no
X;;optional fields
X(define-macro (simulation-object-len) 1)
X
X
X;;ACTUAL-MAKE-BALL returns a ball object
X;;BALL-NUMBER = An index into the ball vector for this ball
X;;MASS = The ball's mass
X;;RADIUS = The ball's radius
X;;PX = The x-coordinate of the ball's initial position
X;;PY = The y-coordinate of the ball's initial position
X;;VX = The x-coordinate of the ball's initial velocity
X;;VY = The y-coordinate of the ball's initial velocity
X(define-macro (actual-make-ball ball-number mass radius px py vx vy)
X  `(make-simulation-object
X    ball-collision-procedure        ;The collision procedure for a ball
X    ,ball-number
X    ,mass
X    ,radius
X    (make-sorted-queue            ;The event queue
X     collision-time-<?)
X    0                    ;Time of last collision
X    ,px                    ;Position of last collision
X    ,py                    ; "
X    ,vx                    ;Velocity following last colliosion
X    ,vy                    ; "
X    '()                    ;No vector of queue records for ball's
X                    ;with smaller numbers
X    '()                    ;No vector of queue records for bumpers
X    '()                    ;No list of balls with larger numbers
X    '()))                ;No global event queue record, yet
X
X(define (make-ball mass radius px py vx vy)
X  (actual-make-ball '() mass radius px py vx vy))
X
X;;BALL-NUMBER returns the index of the given ball
X;;BALL = The ball whose index is to be returned
X(define-macro (ball-number ball)
X  `(vector-ref ,ball ,(simulation-object-len)))
X
X;;SET-BALL-NUMBER! set the index of the given ball to the given value
X;;BALL = The ball whose index is to be set
X;;VALUE = The value to which it is to be set
X(define-macro (set-ball-number! ball value)
X  `(vector-set! ,ball ,(simulation-object-len) ,value))
X
X;;BALL-MASS returns the mass of the given ball
X;;BALL = The ball whose mass is to be returned
X(define-macro (ball-mass ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 1)))
X
X;;BALL-RADIUS returns the radius of the given ball
X;;BALL = The ball whose radius is to be returned
X(define-macro (ball-radius ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 2)))
X
X;;BALL-EVENT-QUEUE returns the sort queue of collision events for the given
X;;ball
X;;BALL = The ball whose event is to be returned
X(define-macro (ball-event-queue ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 3)))
X
X;;BALL-COLLISION-TIME returns the time of the last collision for the given ball
X;;BALL = The ball whose collision time is to be returned
X(define-macro (ball-collision-time ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 4)))
X
X
X;;SET-BALL-COLLISION-TIME! sets the time of the last collision for the given
X;;ball
X;;BALL = The ball whose collision time is to be set
X;;VALUE = The value to which the ball's collision time is to be set
X(define-macro (set-ball-collision-time! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 4) ,value))
X
X;;BALL-COLLISION-X-POSITION returns the x-coordinate of the position  of the
X;;last collision for the given ball
X;;BALL = The ball whose collision position is to be returned
X(define-macro (ball-collision-x-position ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 5)))
X
X;;SET-BALL-COLLISION-X-POSITION! sets the x-coordinate of the position of the
X;;last collision for the given ball
X;;BALL = The ball whose collision position is to be set
X;;VALUE = The value to which the ball's collision position is to be set
X(define-macro (set-ball-collision-x-position! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 5) ,value))
X
X;;BALL-COLLISION-Y-POSITION returns the y-coordinate of the position  of the
X;;last collision for the given ball
X;;BALL = The ball whose collision position is to be returned
X(define-macro (ball-collision-y-position ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 6)))
X
X;;SET-BALL-COLLISION-Y-POSITION! sets the y-coordinate of the position of the
X;;last collision for the given ball
X;;BALL = The ball whose collision position is to be set
X;;VALUE = The value to which the ball's collision position is to be set
X(define-macro (set-ball-collision-y-position! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 6) ,value))
X
X;;BALL-X-VELOCITY returns the x-coordinate of the velocity of the given ball
X;;following its last collision
X;;BALL = The ball whose velocity is to be returned
X(define-macro (ball-x-velocity ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 7)))
X
X;;SET-BALL-X-VELOCITY! sets the x-coordinate of the velocity of the given ball
X;;BALL = The ball whose velocity is to be set
X;;VALUE = The value to which the ball's velocity is to be set
X(define-macro (set-ball-x-velocity! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 7) ,value))
X
X;;BALL-Y-VELOCITY returns the y-coordinate of the velocity  of the given ball
X;;following its last collision
X;;BALL = The ball whose velocity is to be returned
X(define-macro (ball-y-velocity ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 8)))
X
X;;SET-BALL-Y-VELOCITY! sets the y-coordinate of the velocity of the given ball
X;;BALL = The ball whose velocity is to be set
X;;VALUE = The value to which the ball's velocity is to be set
X(define-macro (set-ball-y-velocity! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 8) ,value))
X
X
X;;BALL-BALL-VECTOR returns the vector of queue records for balls with smaller
X;;ball numbers
X;;BALL = The ball whose ball vector is to be returned
X(define-macro (ball-ball-vector ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 9)))
X
X;;SET-BALL-BALL-VECTOR! sets the vector of queue records for balls with smaller
X;;ball numbers
X;;BALL = The ball whose ball vector is to be set
X;;VALUE = The vector to which the field is to be set
X(define-macro (set-ball-ball-vector! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 9) ,value))
X
X;;BALL-BUMPER-VECTOR returns the vector of queue records for bumpers
X;;BALL = The ball whose bumper vector is to be returned
X(define-macro (ball-bumper-vector ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 10)))
X
X;;SET-BALL-BUMPER-VECTOR! sets the vector of queue records for bumpers
X;;BALL = The ball whose bumper vector is to be set
X;;VALUE = The vector to which the field is to be set
X(define-macro (set-ball-bumper-vector! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 10) ,value))
X
X;;BALL-BALL-LIST returns a list of balls with larger ball numbers than the
X;;given ball
X;;BALL = The ball whose ball list is to be returned
X(define-macro (ball-ball-list ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 11)))
X
X;;SET-BALL-BALL-LIST! sets the list of balls with larger ball numbers than the
X;;given ball
X;;BALL = The ball whose ball list is to be set
X;;VALUE = The value to which the ball list is to be set
X(define-macro (set-ball-ball-list! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 11) ,value))
X
X;;BALL-GLOBAL-EVENT-QUEUE-RECORD returns the global event queue record for the
X;;given ball
X;;BALL = The ball whose global event queue record is to be returned
X(define-macro (ball-global-event-queue-record ball)
X  `(vector-ref ,ball ,(+ (simulation-object-len) 12)))
X
X;;SET-BALL-GLOBAL-EVENT-QUEUE-RECORD! set the global event queue record for the
X;;given ball to the given value
X;;BALL = The ball whose global event queue record is to be set
X;;VALUE = The value to which the global event queue record field is to be set
X(define-macro (set-ball-global-event-queue-record! ball value)
X  `(vector-set! ,ball ,(+ (simulation-object-len) 12) ,value))
X
X
X
X;;ACTUAL-MAKE-BUMPER returns a bumper object
X;;BUMPER-NUMBER = An index into the bumper vector for this bumper
X;;X1 = The x-coordiante of one end of the bumper
X;;Y1 = The y-coordiante of one end of the bumper
X;;X2 = The x-coordiante of the other end of the bumper
X;;Y2 = The y-coordiante of the other end of the bumper
X(define-macro (actual-make-bumper bumper-number x1 y1 x2 y2)
X  `(make-simulation-object
X    bumper-collision-procedure        ;The collision procedure for a bumper
X    ,bumper-number
X    ,x1                    ;The bumper endpoints
X    ,y1
X    ,x2
X    ,y2))
X
X(define (make-bumper x1 y1 x2 y2)
X  (actual-make-bumper '() x1 y1 x2 y2))
X
X;;BUMPER-NUMBER returns the index of the given bumper
X;;BUMPER = The bumper whose index is to be returned
X(define-macro (bumper-number bumper)
X  `(vector-ref ,bumper ,(simulation-object-len)))
X
X;;SET-BUMPER-NUMBER! set the index of the given bumper to the given value
X;;BUMPER = The bumper whose index is to be set
X;;VALUE = The value to which it is to be set
X(define-macro (set-bumper-number! bumper value)
X  `(vector-set! ,bumper ,(simulation-object-len) ,value))
X
X;;BUMPER-X1 returns the x-coordinate of one end of the given bumber
X;;BUMPER = the bumper whose x-coordinate is to be returned
X(define-macro (bumper-x1 bumper)
X  `(vector-ref ,bumper ,(1+ (simulation-object-len))))
X
X;;SET-BUMPER-X1! sets the x-coordinate of one end of the given bumber
X;;BUMPER = the bumper whose x-coordinate is to be set
X;;VALUE = The value to which the bumpers x-coordinate is to be set
X(define-macro (set-bumper-x1! bumper value)
X  `(vector-set! ,bumper ,(1+ (simulation-object-len)) ,value))
X
X;;BUMPER-Y1 returns the y-coordinate of one end of the given bumber
X;;BUMPER = the bumper whose y-coordinate is to be returned
X(define-macro (bumper-y1 bumper)
X  `(vector-ref ,bumper ,(+ (simulation-object-len) 2)))
X
X;;SET-BUMPER-Y1! sets the y-coordinate of one end of the given bumber
X;;BUMPER = the bumper whose y-coordinate is to be set
X;;VALUE = The value to which the bumpers y-coordinate is to be set
X(define-macro (set-bumper-y1! bumper value)
X  `(vector-set! ,bumper ,(+ (simulation-object-len) 2) ,value))
X
X;;BUMPER-X2 returns the x-coordinate of the other end of the given bumber
X;;BUMPER = the bumper whose x-coordinate is to be returned
X(define-macro (bumper-x2 bumper)
X  `(vector-ref ,bumper ,(+ (simulation-object-len) 3)))
X
X;;SET-BUMPER-X2! sets the x-coordinate of the other end of the given bumber
X;;BUMPER = the bumper whose x-coordinate is to be set
X;;VALUE = The value to which the bumpers x-coordinate is to be set
X(define-macro (set-bumper-x2! bumper value)
X  `(vector-set! ,bumper ,(+ (simulation-object-len) 3) ,value))
X
X
X;;BUMPER-Y2 returns the y-coordinate of the other end of the given bumber
X;;BUMPER = the bumper whose y-coordinate is to be returned
X(define-macro (bumper-y2 bumper)
X  `(vector-ref ,bumper ,(+ (simulation-object-len) 4)))
X
X;;SET-BUMPER-Y2! sets the y-coordinate of the other end of the given bumber
X;;BUMPER = the bumper whose y-coordinate is to be set
X;;VALUE = The value to which the bumpers y-coordinate is to be set
X(define-macro (set-bumper-y2! bumper value)
X  `(vector-set! ,bumper ,(+ (simulation-object-len) 4) ,value))
X
X;;COLLISION-TIME-<? is a predicate which returns true if the first event queueu
X;;record represents a collision that will take place at an earlier time than
X;;the one for the second event queue record
X;;EVENT-QUEUE-RECORD1 = The first event queue record
X;;EVENT-QUEUE-RECORD2 = The second event queue record
X(define (collision-time-<? event-queue-record1 event-queue-record2)
X  (time-<?
X   (event-queue-record-collision-time
X    event-queue-record1)
X   (event-queue-record-collision-time
X    event-queue-record2)))
X
X;;TIME-<? is a predicate which returns true if the first time is smaller than
X;;the second.  '() represents a time infinitly large.
X(define (time-<? time1 time2)
X  (if (null? time1)
X      #f
X      (if (null? time2)
X      #t
X      (< time1 time2))))
X
X;;SQUARE returns the square of its argument
X(define (square x)
X  (* x x))
X
X
X;;BALL-BALL-COLLISION-TIME returns the time at which the two given balls would
X;;collide if neither interacted with any other objects, '() if never.  This
X;;calculation is performed by setting the distance between the balls to the sum
X;;of their radi and solving for the contact time.
X;;BALL1 = The first ball
X;;BALL2 = The second ball
X(define (ball-ball-collision-time ball1 ball2)
X  (let ((delta-x-velocity        ;Cache the difference in the ball's
X     ( - (ball-x-velocity ball2)    ;velocities,
X         (ball-x-velocity ball1)))
X    (delta-y-velocity
X     ( - (ball-y-velocity ball2)
X         (ball-y-velocity ball1)))
X    (radius-sum            ;the sum of their radi,
X     (+ (ball-radius ball1)
X        (ball-radius ball2)))
X    (alpha-x            ;and common subexpressions in the time
X     (-                ;equation
X      (- (ball-collision-x-position
X          ball2)
X         (ball-collision-x-position
X          ball1))
X      (-
X       (* (ball-x-velocity ball2)
X          (ball-collision-time
X           ball2))
X       (* (ball-x-velocity ball1)
X          (ball-collision-time
X           ball1)))))
X    (alpha-y
X     (-
X      (- (ball-collision-y-position
X          ball2)
X         (ball-collision-y-position
X          ball1))
X      (-
X       (* (ball-y-velocity ball2)
X          (ball-collision-time
X           ball2))
X       (* (ball-y-velocity ball1)
X          (ball-collision-time
X           ball1))))))
X    (let* ((delta-velocity-magnitude-squared
X        (+ (square
X        delta-x-velocity)
X           (square
X        delta-y-velocity)))
X       (discriminant
X        (- (* (square radius-sum)
X          delta-velocity-magnitude-squared)
X           (square
X        (- (* delta-y-velocity
X              alpha-x)
X           (* delta-x-velocity
X              alpha-y))))))
X
X
X      (if (or (negative? discriminant)    ;If the balls don't colloide:
X          (zero?
X           delta-velocity-magnitude-squared))
X      '()                ;Return infinity
X      (let ((time            ;Else, calculate the collision time
X         (/
X          (- 0
X             (+ (sqrt discriminant)
X            (+
X             (* delta-x-velocity
X                alpha-x)
X             (* delta-y-velocity
X                alpha-y))))
X          (+ (square
X              delta-x-velocity)
X             (square
X              delta-y-velocity)))))
X        (if (and            ;If the balls collide in the future:
X         (time-<?
X          (ball-collision-time
X           ball1)
X          time)
X         (time-<?
X          (ball-collision-time
X           ball2)
X          time))
X        time            ;Return the collision time
X        '()))))))        ;Else, return that they never collide
X
X;;BALL-BUMPER-COLLISION-TIME returns the time at which the given ball would
X;;collide with the given bumper if the ball didn't interacted with any other
X;;objects, '() if never.  This is done by first calculating the time at which
X;;the ball would collide with a bumper of infinite length and then checking if
X;;the collision position represents a portion of the actual bumper.
X;;BALL = The ball
X;;BUMPER = The bumper
X(define (ball-bumper-collision-time ball bumper)
X  (let ((delta-x-bumper            ;Collision time with the bumper of
X     (- (bumper-x2 bumper)        ;infinite extent is calculated by
X        (bumper-x1 bumper)))    ;setting the distance between the ball
X    (delta-y-bumper            ;and the bumper to be the radius of the
X     (- (bumper-y2 bumper)        ;ball and solving for the time.  The
X        (bumper-y1 bumper))))    ;distance is calculated by |aXb|/|a|,
X    (let ((bumper-length-squared    ;where 'a' is the vector from one end
X       (+ (square delta-x-bumper)    ;of the bumper to the other and 'b' is
X          (square delta-y-bumper)))    ;the vector from the first end of the
X      (denominator            ;bumper to the center of the ball
X       (- (* (ball-y-velocity ball)
X         delta-x-bumper)
X          (* (ball-x-velocity ball)
X         delta-y-bumper))))
X      (if (zero? denominator)        ;If the ball's motion is parallel to
X                    ;the bumper:
X      '()                ;Return infinity
X      (let ((delta-t        ;Calculate the collision time
X         (-
X          (/
X           (+
X            (*
X             (-    (ball-collision-x-position
X             ball)
X            (bumper-x1 bumper))
X             delta-y-bumper)
X            (*
X             (- (ball-collision-y-position
X             ball)
X            (bumper-y1 bumper))
X             delta-x-bumper))
X           denominator)
X          (/
X           (* (ball-radius
X               ball)
X              (sqrt
X               bumper-length-squared))
X           (abs denominator)))))
X        (if (not (positive?        ;If the ball is moving away from the
X              delta-t))        ;bumper:
X        '()            ;Return infinity
X
X
X        (let ((ball-x-contact    ;Whether the ball contacts the actual
X               (+ (ball-collision-x-position ;bumper of limited extent
X               ball)    ;will be determined by comparing |b.a|
X              (* (ball-x-velocity ;with |a|^2
X                  ball)
X                 delta-t)))
X              (ball-y-contact
X               (+ (ball-collision-y-position
X               ball)
X              (* (ball-y-velocity
X                  ball)
X                 delta-t))))
X          (let ((delta-x-ball
X             (- ball-x-contact
X                (bumper-x1
X                 bumper)))
X            (delta-y-ball
X             (- ball-y-contact
X                (bumper-y1
X                 bumper))))
X            (let ((dot-product
X               (+
X                (* delta-x-ball
X                   delta-x-bumper)
X                (* delta-y-ball
X                   delta-y-bumper))))
X              (if (or        ;If the ball misses the bumper on
X               (negative?    ;either end:
X                dot-product)
X               (> dot-product
X                  bumper-length-squared))
X              '()        ;Return infinity
X              (+ delta-t    ;Else, return the contact time
X                 (ball-collision-time
X                  ball))))))))))))
X
X
X;;BALL-COLLISION-PROCEDURE calculates the new velocities of the given balls
X;;based on their collision at the given time.  Also, tells all other balls
X;;about the new trajectories of these balls so they can update their event
X;;queues
X;;BALL1 = The first ball
X;;BALL2 = The second ball
X;;COLLISION-TIME = The collision time
X;;GLOBAL-EVENT-QUEUE = The global queue of earliest events for each ball
X(define (ball-collision-procedure ball1 ball2 collision-time
X                  global-event-queue)
X  (queue-remove                ;Remove the earliest event associated
X   (ball-global-event-queue-record    ;with each ball from the global event
X    ball1))                ;queue
X  (queue-remove
X   (ball-global-event-queue-record
X    ball2))
X  (let ((ball1-collision-x-position    ;Calculate the positions of both balls
X     (+ (ball-collision-x-position    ;when they collide
X         ball1)
X        (* (ball-x-velocity
X        ball1)
X           (- collision-time
X          (ball-collision-time
X           ball1)))))
X    (ball1-collision-y-position
X     (+ (ball-collision-y-position
X         ball1)
X        (* (ball-y-velocity
X        ball1)
X           (- collision-time
X          (ball-collision-time
X           ball1)))))
X    (ball2-collision-x-position
X     (+ (ball-collision-x-position
X         ball2)
X        (* (ball-x-velocity
X        ball2)
X           (- collision-time
X          (ball-collision-time
X           ball2)))))
X    (ball2-collision-y-position
X     (+ (ball-collision-y-position
X         ball2)
X        (* (ball-y-velocity
X        ball2)
X           (- collision-time
X          (ball-collision-time
X           ball2))))))
X    (let ((delta-x            ;Calculate the displacements of the
X       (- ball2-collision-x-position ;centers of the two balls
X          ball1-collision-x-position))
X      (delta-y
X       (- ball2-collision-y-position
X          ball1-collision-y-position)))
X
X
X      (let* ((denominator        ;Calculate the angle of the line
X          (sqrt (+ (square        ;joining the centers at the collision
X            delta-x)    ;time with the x-axis  (this line is
X               (square        ;the normal to the balls at the
X            delta-y))))    ;collision point)
X         (cos-theta
X          (/ delta-x denominator))
X         (sin-theta
X          (/ delta-y denominator)))
X      (let ((ball1-old-normal-velocity ;Convert the velocities of the balls
X         (+ (* (ball-x-velocity    ;into the coordinate system defined by
X            ball1)        ;the normal and tangential lines at
X               cos-theta)    ;the collision point
X            (* (ball-y-velocity
X            ball1)
X               sin-theta)))
X        (ball1-tang-velocity
X         (- (* (ball-y-velocity
X            ball1)
X               cos-theta)
X            (* (ball-x-velocity
X            ball1)
X               sin-theta)))
X        (ball2-old-normal-velocity
X         (+ (* (ball-x-velocity
X            ball2)
X               cos-theta)
X            (* (ball-y-velocity
X            ball2)
X               sin-theta)))
X        (ball2-tang-velocity
X         (- (* (ball-y-velocity
X            ball2)
X               cos-theta)
X            (* (ball-x-velocity
X            ball2)
X               sin-theta)))
X        (mass1 (ball-mass
X            ball1))
X        (mass2 (ball-mass
X            ball2)))
X        (let ((ball1-new-normal-velocity ;Calculate the new velocities
X           (/            ;following the collision (the
X            (+            ;tangential velocities are unchanged
X             (*            ;because the balls are assumed to be
X              (* 2        ;frictionless)
X             mass2)
X              ball2-old-normal-velocity)
X             (*
X              (- mass1 mass2)
X              ball1-old-normal-velocity))
X            (+ mass1 mass2)))
X
X
X          (ball2-new-normal-velocity
X           (/
X            (+
X             (*
X              (* 2
X             mass1)
X              ball1-old-normal-velocity)
X             (*
X              (- mass2 mass1)
X              ball2-old-normal-velocity))
X            (+ mass1 mass2))))
X          (set-ball-x-velocity!    ;Store data about the collision in the
X           ball1            ;structure for each ball after
X           (- (* ball1-new-normal-velocity ;converting the information back
X             cos-theta)        ;to the x,y frame
X          (* ball1-tang-velocity
X             sin-theta)))
X          (set-ball-y-velocity!
X           ball1
X           (+ (* ball1-new-normal-velocity
X             sin-theta)
X          (* ball1-tang-velocity
X             cos-theta)))
X          (set-ball-x-velocity!
X           ball2
X           (- (* ball2-new-normal-velocity
X             cos-theta)
X          (* ball2-tang-velocity
X             sin-theta)))
X          (set-ball-y-velocity!
X           ball2
X           (+ (* ball2-new-normal-velocity
X             sin-theta)
X          (* ball2-tang-velocity
X             cos-theta)))
X          (set-ball-collision-time!
X           ball1
X           collision-time)
X          (set-ball-collision-time!
X           ball2
X           collision-time)
X          (set-ball-collision-x-position!
X           ball1
X           ball1-collision-x-position)
X          (set-ball-collision-y-position!
X           ball1
X           ball1-collision-y-position)
X          (set-ball-collision-x-position!
X           ball2
X           ball2-collision-x-position)
X          (set-ball-collision-y-position!
X           ball2
X           ball2-collision-y-position))))))
X
X
X  (newline)
X  (display "Ball ")
X  (display (ball-number ball1))
X  (display " collides with ball ")
X  (display (ball-number ball2))
X  (display " at time ")
X  (display (ball-collision-time ball1))
X  (newline)
X  (display "   Ball ")
X  (display (ball-number ball1))
X  (display " has a new velocity of ")
X  (display (ball-x-velocity ball1))
X  (display ",")
X  (display (ball-y-velocity ball1))
X  (display " starting at ")
X  (display (ball-collision-x-position ball1))
X  (display ",")
X  (display (ball-collision-y-position ball1))
X  (newline)
X  (display "   Ball ")
X  (display (ball-number ball2))
X  (display " has a new velocity of ")
X  (display (ball-x-velocity ball2))
X  (display ",")
X  (display (ball-y-velocity ball2))
X  (display " starting at ")
X  (display (ball-collision-x-position ball2))
X  (display ",")
X  (display (ball-collision-y-position ball2))
X
X  (recalculate-collisions ball1 global-event-queue)
X  (recalculate-collisions ball2 global-event-queue))
X
X
X;;BUMPER-COLLISION-PROCEDURE calculates the new velocity of the given ball
X;;following its collision with the given bumper at the given time.  Also, tells
X;;other balls about the new trajectory of the given ball so they can update
X;;their event queues.
X;;BALL = The ball
X;;BUMPER = The bumper
X;;COLLISION-TIME = The collision time
X;;GLOBAL-EVENT-QUEUE = The global queue of earliest events for each ball
X(define (bumper-collision-procedure ball bumper collision-time
X                    global-event-queue)
X  (queue-remove                ;Remove the earliest event associated
X   (ball-global-event-queue-record    ;with the ball from the global event
X    ball))                ;queue
X  (let ((delta-x-bumper            ;Compute the bumper's delta-x
X     (- (bumper-x2 bumper)
X        (bumper-x1 bumper)))
X    (delta-y-bumper            ;delta-y
X     (- (bumper-y2 bumper)
X        (bumper-y1 bumper))))
X    (let ((bumper-length        ;length
X       (sqrt
X        (+ (square
X        delta-x-bumper)
X           (square
X        delta-y-bumper)))))
X      (let ((cos-theta            ;and cosine and sine of its angle with
X         (/ delta-x-bumper        ;respect to the positive x-axis
X        bumper-length))
X        (sin-theta
X         (/ delta-y-bumper
X        bumper-length))
X        (x-velocity            ;Cache the ball's velocity in the x,y
X         (ball-x-velocity ball))    ;frame
X        (y-velocity
X         (ball-y-velocity ball)))
X    (let ((tang-velocity        ;Calculate the ball's velocity in the
X           (+ (* x-velocity        ;bumper frame
X             cos-theta)
X          (* y-velocity
X             sin-theta)))
X          (normal-velocity
X           (- (* y-velocity
X             cos-theta)
X          (* x-velocity
X             sin-theta))))
X
X
X      (set-ball-collision-x-position! ;Store the collision position
X       ball
X       (+ (ball-collision-x-position
X           ball)
X          (* (- collision-time
X            (ball-collision-time
X             ball))
X         (ball-x-velocity
X          ball))))
X      (set-ball-collision-y-position!
X       ball
X       (+ (ball-collision-y-position
X           ball)
X          (* (- collision-time
X            (ball-collision-time
X             ball))
X         (ball-y-velocity
X          ball))))
X      (set-ball-x-velocity!        ;Calculate the new velocity in the
X       ball                ;x,y frame based on the fact that
X       (+ (* tang-velocity        ;tangential velocity is unchanged and
X         cos-theta)        ;the normal velocity is inverted when
X          (* normal-velocity    ;the ball collides with the bumper
X         sin-theta)))
X      (set-ball-y-velocity!
X       ball
X       (- (* tang-velocity
X         sin-theta)
X          (* normal-velocity
X         cos-theta)))
X      (set-ball-collision-time!
X       ball
X       collision-time)))))
X  (newline)
X  (display "Ball ")
X  (display (ball-number ball))
X  (display " collides with bumper ")
X  (display (bumper-number bumper))
X  (display " at time ")
X  (display (ball-collision-time ball))
X  (newline)
X  (display "   Ball ")
X  (display (ball-number ball))
X  (display " has a new velocity of ")
X  (display (ball-x-velocity ball))
X  (display ",")
X  (display (ball-y-velocity ball))
X  (display " starting at ")
X  (display (ball-collision-x-position ball))
X  (display ",")
X  (display (ball-collision-y-position ball))
X
X  (recalculate-collisions ball global-event-queue))
X
X
X;;RECALCULATE-COLLISIONS removes all old collisions for the given ball from
X;;all other balls' event queues and calcultes new collisions for these balls
X;;and places them on the event queues.  Also, updates the global event queue if
X;;the recalculation of the collision effects the earliest collision for any
X;;other balls.
X;;BALL = The ball whose collisions are being recalculated
X;;GLOBAL-EVENT-QUEUE = The global queue of earliest events for each ball
X(define (recalculate-collisions ball global-event-queue)
X  (clear-queue (ball-event-queue    ;Clear the queue of events for this
X        ball))            ;ball as they have all changed
X  (let ((event-queue            ;Calculate all ball collision events
X     (ball-event-queue ball)))    ;with balls of lower number
X    (let ((ball-vector
X       (ball-ball-vector ball)))
X      (do ((i (-1+ (ball-number ball))
X          (-1+ i)))
X      ((negative? i))
X    (let ((ball2-queue-record
X           (vector-ref
X        ball-vector
X        i)))
X      (set-event-queue-record-collision-time!
X       ball2-queue-record
X       (ball-ball-collision-time
X        ball
X        (event-queue-record-object
X         ball2-queue-record)))
X      (queue-insert
X       event-queue
X       ball2-queue-record))))
X    (let ((bumper-vector        ;Calculate all bumper collision events
X       (ball-bumper-vector ball)))
X      (do ((i (-1+ (vector-length
X            bumper-vector))
X          (-1+ i)))
X      ((negative? i))
X    (let ((bumper-queue-record
X           (vector-ref
X        bumper-vector
X        i)))
X      (set-event-queue-record-collision-time!
X       bumper-queue-record
X       (ball-bumper-collision-time
X        ball
X        (event-queue-record-object
X         bumper-queue-record)))
X      (queue-insert
X       event-queue
X       bumper-queue-record))))
X
X
X    (let ((global-queue-record        ;Get the global event queue record
X       (ball-global-event-queue-record ;for this ball
X        ball)))
X      (set-event-queue-record-collision-time! ;Set the new earliest event time
X       global-queue-record        ;for this ball
X       (if (empty-queue? event-queue)
X       '()
X       (event-queue-record-collision-time
X        (queue-smallest event-queue))))
X      (queue-insert            ;Enqueue on the global event queue
X       global-event-queue        ;the earliest event between this ball
X       global-queue-record)))        ;and any ball of lower number or any
X                    ;bumper
X  (for-each                ;For each ball on the ball list:
X   (lambda (ball2)
X     (let ((ball2-event-queue
X        (ball-event-queue ball2)))
X       (let ((alter-global-event-queue?    ;Set flag to update global event queue
X          (and            ;if the earliest event for ball2 was
X           (not (empty-queue?    ;with the deflected ball
X             ball2-event-queue))
X           (eq? ball
X            (event-queue-record-object
X             (queue-smallest
X              ball2-event-queue)))))
X         (ball-event-queue-record    ;Get the queue record for the deflected
X          (vector-ref        ;ball for this ball
X           (ball-ball-vector
X        ball2)
X           (ball-number ball))))
X     (queue-remove            ;Remove the queue record for the
X      ball-event-queue-record)    ;deflected ball
X     (set-event-queue-record-collision-time! ;Recalculate the collision
X      ball-event-queue-record    ;time for this ball and the deflected
X      (ball-ball-collision-time    ;ball
X       ball
X       ball2))
X     (queue-insert            ;Enqueue the new collision event
X      ball2-event-queue
X      ball-event-queue-record)
X     (if (or alter-global-event-queue? ;If the earliest collision event for
X         (eq? ball        ;this ball has changed:
X              (event-queue-record-object
X               (queue-smallest
X            ball2-event-queue))))
X         (let ((queue-record    ;Remove the old event from the global
X            (ball-global-event-queue-record ;event queue and replace it
X             ball2)))        ;with the new event
X           (set-event-queue-record-collision-time!
X        queue-record
X        (event-queue-record-collision-time
X         (queue-smallest
X          ball2-event-queue)))
X           (queue-remove
X        queue-record)
X           (queue-insert
X        global-event-queue
X        queue-record))))))
X   (ball-ball-list ball)))
X
X
X;;SIMULATE performs the billiard ball simulation for the given ball list and
X;;bumper list until the specified time.
X;;BALL-LIST = A list of balls
X;;BUMPER-LIST = A list of bumpers
X;;END-TIME = The time at which the simulation is to terminate
X(define (simulate ball-list bumper-list end-time)
X  (let ((num-of-balls            ;Cache the number of balls and bumpers
X     (length ball-list))
X    (num-of-bumpers
X     (length bumper-list))
X    (global-event-queue        ;Build the global event queue
X     (make-sorted-queue
X      collision-time-<?)))
X    (let ((complete-ball-vector        ;Build a vector for the balls
X       (make-vector
X        num-of-balls)))
X      (let loop ((ball-num 0)        ;For each ball:
X         (ball-list ball-list))
X    (if (not (null? ball-list))
X        (let ((ball (car ball-list)))
X          (set-ball-number!        ;Store the ball's number
X           ball
X           ball-num)
X          (vector-set!        ;Place it in the ball vector
X           complete-ball-vector
X           ball-num
X           ball)
X          (set-ball-ball-list!    ;Save the list of balls with ball
X           ball            ;numbers greater than the current ball
X           (cdr ball-list))
X          (display-ball-state
X           ball)
X          (loop
X           (1+ ball-num)
X           (cdr ball-list)))))
X      (let loop ((bumper-num 0)        ;For each bumper:
X         (bumper-list
X          bumper-list))
X    (if (not (null? bumper-list))
X        (sequence
X          (set-bumper-number!    ;Store the bumper's number
X           (car bumper-list)
X           bumper-num)
X          (display-bumper-state
X           (car bumper-list))
X          (loop
X           (1+ bumper-num)
X           (cdr bumper-list)))))
X
X      (do ((ball-num 0 (1+ ball-num)))    ;For each ball:
X      ((= ball-num num-of-balls))
X    (let* ((ball (vector-ref    ;Cache a reference to the ball
X              complete-ball-vector
X              ball-num))
X           (ball-vector        ;Build a vector for the queue records
X        (make-vector        ;of balls with smaller numbers than
X         ball-num))        ;this ball
X           (bumper-vector        ;Build a vector for the queue records
X        (make-vector        ;of bumpers
X         num-of-bumpers))
X           (event-queue        ;Build an event queue for this ball
X        (ball-event-queue
X         ball)))
X      (set-ball-ball-vector!    ;Install the vector of ball queue
X       ball                ;records
X       ball-vector)
X      (do ((i 0 (1+ i)))        ;For each ball of smaller number than
X          ((= i ball-num))    ;the current ball:
X        (let* ((ball2        ;Cache the ball
X            (vector-ref
X             complete-ball-vector
X             i))
X               (queue-record    ;Create a queue record for this ball
X            (make-event-queue-record ;based on the collision time
X             '()        ;of the two balls
X             '()
X             ball2
X             (ball-ball-collision-time
X              ball
X              ball2))))
X          (vector-set!        ;Install the queue record in the ball
X           ball-vector        ;vector for this ball
X           i
X           queue-record)
X          (queue-insert        ;Insert the queue record into the event
X           event-queue        ;queue for this ball
X           queue-record)))
X
X      (set-ball-bumper-vector!    ;Install the vector of bumper queue
X       ball                ;records
X       bumper-vector)
X      (let loop ((bumper-num 0)
X             (bumper-list
X              bumper-list))
X        (if (not (null? bumper-list))
X        (let* ((bumper        ;Cache the bumper
X            (car
X             bumper-list))
X               (queue-record    ;Create a queue record for this bumper
X            (make-event-queue-record ;based on the collision time
X             '()        ;of the current ball and this bumper
X             '()
X             bumper
X             (ball-bumper-collision-time
X              ball
X              bumper))))
X          (vector-set!        ;Install the queue record in the bumper
X           bumper-vector    ;vector for this ball
X           bumper-num
X           queue-record)
X          (queue-insert        ;Insert the queue record into the event
X           event-queue        ;queue for this ball
X           queue-record)
X          (loop
X           (1+ bumper-num)
X           (cdr bumper-list)))))
X      (let ((queue-record        ;Build a global event queue record for
X         (make-event-queue-record ;the earliest event on this ball's
X          '()            ;event queue
X          '()
X          ball
X          (if (empty-queue?
X               event-queue)
X              '()
X              (event-queue-record-collision-time
X               (queue-smallest
X            event-queue))))))
X        (set-ball-global-event-queue-record! ;Store this queue record in
X         ball            ;the frame for this ball
X         queue-record)
X        (queue-insert        ;Insert this queue record in the global
X         global-event-queue        ;event queue
X         queue-record)))))
X    (actually-simulate            ;Now that all of the data structures
X     global-event-queue            ;have been built, actually start the
X     end-time)))            ;simulation
X
X
X;;DISPLAY-BALL-STATE displays the ball number, mass, radius, position, and
X;;velocity of the given ball
X;;BALL = The ball whose state is to be displayed
X(define (display-ball-state ball)
X  (newline)
X  (display "Ball ")
X  (display (ball-number ball))
X  (display " has mass ")
X  (display (ball-mass ball))
X  (display " and radius ")
X  (display (ball-radius ball))
X  (newline)
X  (display "   Its position at time ")
X  (display (ball-collision-time ball))
X  (display " was ")
X  (display (ball-collision-x-position ball))
X  (display ",")
X  (display (ball-collision-y-position ball))
X  (display " and its velocity is ")
X  (display (ball-x-velocity ball))
X  (display ",")
X  (display (ball-y-velocity ball)))
X
X;;DISPLAY-BUMPER-STATE displays the bumper number and position of the given
X;;bumper
X;;BUMPER = The bumper whose state is to be displayed
X(define (display-bumper-state bumper)
X  (newline)
X  (display "Bumper ")
X  (display (bumper-number bumper))
X  (display " extends from ")
X  (display (bumper-x1 bumper))
X  (display ",")
X  (display (bumper-y1 bumper))
X  (display " to ")
X  (display (bumper-x2 bumper))
X  (display ",")
X  (display (bumper-y2 bumper)))
X
X
X;;ACTUALLY-SIMULATE performs the actual billiard ball simulation
X;;GLOBAL-EVENT-QUEUE = The global queue of earliest events for each ball.
X;;                     Contains a single event for each ball which is the
X;;                     earliest collision it would have with a ball of a
X;;                     smaller number or a bumper, if no other collisions took
X;;                     place first.
X;;END-TIME = The time at which the simulation should be terminated
X(define (actually-simulate global-event-queue end-time)
X  (letrec ((loop
X        (lambda ()
X          (let* ((record        ;Get the globally earliest event and
X              (queue-smallest    ;its time
X               global-event-queue))
X             (collision-time
X              (event-queue-record-collision-time
X               record)))
X        (if (not        ;If this event happens before the
X             (time-<?        ;simulation termination time:
X              end-time
X              collision-time))
X            (let* ((ball    ;Get the ball involved in the event,
X                (event-queue-record-object
X                 record))
X               (ball-queue    ;the queue of events for that ball,
X                (ball-event-queue
X                 ball))
X               (other-object ;and the first object with which the
X                (event-queue-record-object ;ball interacts
X                 (queue-smallest
X                  ball-queue))))
X              ((simulation-object-collision-procedure ;Process this
X            other-object)    ;globally earliest collision
X               ball
X               other-object
X               collision-time
X               global-event-queue)
X              (loop)))))))    ;Process the next interaction
X    (loop)))
X
X
X(require 'cscheme)
X(set! autoload-notify? #f)
X
X        (simulate
X         (list (make-ball 2 1 9 5 -1 -1)
X               (make-ball 4 2 2 5 1 -1))
X         (list (make-bumper 0 0 0 10)
X               (make-bumper 0 0 10 0)
X               (make-bumper 0 10 10 10)
X               (make-bumper 10 0 10 10))
X         100)
END_OF_tst/billiard
if test 46118 -ne `wc -c <tst/billiard`; then
    echo shar: \"tst/billiard\" unpacked with wrong size!
fi
# end of overwriting check
fi
if test -f lib/xlib/examples/properties -a "${1}" != "-c" ; then
  echo shar: Will not over-write existing file \"lib/xlib/examples/properties\"
else
echo shar: Extracting \"lib/xlib/examples/properties\" \(969 characters\)
sed "s/^X//" >lib/xlib/examples/properties <<'END_OF_lib/xlib/examples/properties'
X;;; -*-Scheme-*-
X;;;
X;;; Display all properties of all windows (with name, type, format,
X;;; and data).
X
X(require 'xlib)
X
X(define (properties)
X  (let ((dpy (open-display)))
X    (unwind-protect
X     (let* ((w (car (query-tree (display-root-window dpy))))
X        (l (map (lambda (win) (cons win (list-properties win)))
X            (cons (display-root-window dpy) (vector->list w))))
X        (tab (lambda (obj n)
X           (let* ((s (format #f "~s" obj))
X              (n (- n (string-length s))))
X             (display s)
X             (if (positive? n)
X             (do ((i 0 (1+ i))) ((= i n)) (display #\space)))))))
X       (for-each
X    (lambda (w)
X      (format #t "Window ~s:~%" (car w))
X      (for-each
X       (lambda (p)
X         (tab (atom-name dpy p) 20)
X         (display "= ")
X         (let ((p (get-property (car w) p #f 0 20 #f)))
X           (tab (atom-name dpy (car p)) 18)
X           (tab (cadr p) 3)
X           (format #t "~s~%" (caddr p))))
X       (vector->list (cdr w)))
X      (newline))
X    l))
X     (close-display dpy))))
X
X(properties)
END_OF_lib/xlib/examples/properties
if test 969 -ne `wc -c <lib/xlib/examples/properties`; then
    echo shar: \"lib/xlib/examples/properties\" unpacked with wrong size!
fi
# end of overwriting check
fi
if test -f lib/xlib/examples/track -a "${1}" != "-c" ; then
  echo shar: Will not over-write existing file \"lib/xlib/examples/track\"
else
echo shar: Extracting \"lib/xlib/examples/track\" \(1062 characters\)
sed "s/^X//" >lib/xlib/examples/track <<'END_OF_lib/xlib/examples/track'
X;;; -*-Scheme-*-
X
X(require 'xlib)
X
X(define (track)
X  (let* ((dpy (open-display))
X     (root (display-root-window dpy))
X     (gc (make-gcontext (window root)
X                (function 'xor)
X                (foreground (black-pixel dpy))
X                (subwindow-mode 'include-inferiors)))
X     (lx 0) (ly 0) (lw 0) (lh 0)
X     (move-outline
X      (lambda (x y w h)
X        (if (not (and (= x lx) (= y ly) (= w lw) (= h lh)))
X        (begin
X          (draw-rectangle root gc lx ly lw lh)
X          (draw-rectangle root gc x y w h)
X          (set! lx x) (set! ly y)
X          (set! lw w) (set! lh h))))))
X    (unwind-protect
X     (case (grab-pointer root #f '(pointer-motion button-press)
X             #f #f 'none 'none 'now)
X       (success
X    (with-server-grabbed dpy
X      (draw-rectangle root gc lx ly lw lh)
X      (display-flush-output dpy)
X      (handle-events dpy
X        (motion-notify
X         (lambda (event root win subwin time x y . rest)
X           (move-outline x y 300 300) #f))
X        (else (lambda args #t)))))
X       (else
X    (format #t "Not grabbed!~%")))
X     (begin
X       (draw-rectangle root gc lx ly lw lh)
X       (close-display dpy)))))
X
X(track)
END_OF_lib/xlib/examples/track
if test 1062 -ne `wc -c <lib/xlib/examples/track`; then
    echo shar: \"lib/xlib/examples/track\" unpacked with wrong size!
fi
# end of overwriting check
fi
if test -f lib/xlib/examples/picture -a "${1}" != "-c" ; then
  echo shar: Will not over-write existing file \"lib/xlib/examples/picture\"
else
echo shar: Extracting \"lib/xlib/examples/picture\" \(2425 characters\)
sed "s/^X//" >lib/xlib/examples/picture <<'END_OF_lib/xlib/examples/picture'
X;;; -*-Scheme-*-
X
X;;; -*- Mode:Lisp; Package:XLIB; Syntax:COMMON-LISP; Base:10; Lowercase:T -*-
X
X;;; CLX - Point Graphing demo program
X
X;;; Copyright (C) 1988 Michael O. Newton ([e-mail])
X
X;;; Permission is granted to any individual or institution to use, copy,
X;;; modify, and distribute this software, provided that this complete
X;;; copyright and permission notice is maintained, intact, in all copies and
X;;; supporting documentation.
X
X;;; The author provides this software "as is" without express or
X;;; implied warranty.
X
X;;; This routine plots the recurrance
X;;;      x <- y(1+sin(0.7x)) - 1.2(|x|)^.5
X;;;      y <- .21 - x
X;;; As described in a ?? 1983 issue of the Mathematical Intelligencer
X;;; It has ONLY been tested under X.V11R2 on a Sun3 running KCL
X
X(require 'xlib)
X
X(define (picture point-count)
X  (let* ((dpy (open-display))
X     (width 600)
X     (height 600)
X     (black (black-pixel dpy))
X     (white (white-pixel dpy))
X     (root (display-root-window dpy))
X     (win (make-window (parent root) (background-pixel white)
X               (event-mask '(exposure button-press))
X               (width width) (height height)))
X     (gc (make-gcontext (window win)
X                (background white) (foreground black))))
X    (map-window win)
X    (unwind-protect
X     (handle-events dpy
X       (expose
X    (lambda ignore
X      (clear-window win)
X      (draw-points win gc point-count 0.0 0.0 (* width 0.5) (* height 0.5))
X      (draw-poly-text win gc 10 10 (translate "Click a button to exit")
X              '1-byte)
X      #f))
X       (else (lambda ignore #t)))
X     (close-display dpy))))
X
X;;; Draw points.  These should maybe be put into a an array so that they do
X;;; not have to be recomputed on exposure.  X assumes points are in the range
X;;; of width x height, with 0,0 being upper left and 0,H being lower left.
X;;;      x <- y(1+sin(0.7x)) - 1.2(|x|)^.5
X;;;      y <- .21 - x
X;;; hw and hh are half-width and half-height of screen
X
X(define (draw-points win gc count x y hw hh)
X  (if (zero? (modulo count 100))
X      (display-flush-output (window-display win)))
X  (if (not (zero? count))
X      (let ((xf (floor (* (+ 1.2 x) hw ))) ; These lines center the picture
X        (yf (floor (* (+ 0.5 y) hh ))))
X    (draw-point win gc xf yf)
X    (draw-points win gc (1- count)
X             (- (* y (1+ (sin (* 0.7 x)))) (* 1.2 (sqrt (abs x))))
X             (- 0.21 x)
X             hw hh))))
X
X(define (translate string)
X  (list->vector (map char->integer (string->list string))))
X
X(picture 10000)
END_OF_lib/xlib/examples/picture
if test 2425 -ne `wc -c <lib/xlib/examples/picture`; then
    echo shar: \"lib/xlib/examples/picture\" unpacked with wrong size!
fi
# end of overwriting check
fi
if test -f lib/xlib/examples/useful -a "${1}" != "-c" ; then
  echo shar: Will not over-write existing file \"lib/xlib/examples/useful\"
else
echo shar: Extracting \"lib/xlib/examples/useful\" \(567 characters\)
sed "s/^X//" >lib/xlib/examples/useful <<'END_OF_lib/xlib/examples/useful'
X;;; -*-Scheme-*-
X
X(require 'xlib)
X
X(define dpy
X  (open-display))
X
X(define (f)
X  (display-wait-output dpy #t))
X
X(define root
X  (display-root-window dpy))
X
X(define cmap
X  (display-colormap dpy))
X
X(define white (white-pixel dpy))
X(define black (black-pixel dpy))
X
X(define rgb-white (query-color cmap white))
X(define rgb-black (query-color cmap black))
X
X(define win
X  (make-window (parent root)
X           (width 300) (height 300)
X           (background-pixel white)))
X
X(define gc (make-gcontext
X        (window win)
X        (background white) (foreground black)))
X
X(map-window win)
END_OF_lib/xlib/examples/useful
if test 567 -ne `wc -c <lib/xlib/examples/useful`; then
    echo shar: \"lib/xlib/examples/useful\" unpacked with wrong size!
fi
# end of overwriting check
fi
if test -f lib/xlib/pixel.c -a "${1}" != "-c" ; then
  echo shar: Will not over-write existing file \"lib/xlib/pixel.c\"
else
echo shar: Extracting \"lib/xlib/pixel.c\" \(1332 characters\)
sed "s/^X//" >lib/xlib/pixel.c <<'END_OF_lib/xlib/pixel.c'
X#include "xlib.h"
X
XGeneric_Predicate (Pixel);
X
XGeneric_Simple_Equal (Pixel, PIXEL, pix);
X
XGeneric_Print (Pixel, "#[pixel 0x%lx]", PIXEL(x)->pix);
X
XObject Make_Pixel (val) unsigned long val; {
X    register char *p;
X    Object pix;
X
X    pix = Find_Object (T_Pixel, (GENERIC)0, Match_X_Obj, val);
X    if (Nullp (pix)) {
X    p = Get_Bytes (sizeof (struct S_Pixel));
X    SET (pix, T_Pixel, (struct S_Pixel *)p);
X    PIXEL(pix)->tag = Null;
X    PIXEL(pix)->pix = val;
X    Register_Object (pix, (GENERIC)0, (PFO)0, 0);
X    }
X    return pix;
X}
X
Xunsigned long Get_Pixel (p) Object p; {
X    Check_Type (p, T_Pixel);
X    return PIXEL(p)->pix;
X}
X
Xstatic Object P_Pixel_Value (p) Object p; {
X    return Make_Unsigned ((unsigned)Get_Pixel (p));
X}
X
Xstatic Object P_Black_Pixel (d) Object d; {
X    Check_Type (d, T_Display);
X    return Make_Pixel (BlackPixel (DISPLAY(d)->dpy,
X    DefaultScreen (DISPLAY(d)->dpy)));
X}
X
Xstatic Object P_White_Pixel (d) Object d; {
X    Check_Type (d, T_Display);
X    return Make_Pixel (WhitePixel (DISPLAY(d)->dpy,
X    DefaultScreen (DISPLAY(d)->dpy)));
X}
X
Xinit_xlib_pixel () {
X    Generic_Define (Pixel, "pixel", "pixel?");
X    Define_Primitive (P_Pixel_Value,   "pixel-value",    1, 1, EVAL);
X    Define_Primitive (P_Black_Pixel,   "black-pixel",    1, 1, EVAL);
X    Define_Primitive (P_White_Pixel,   "white-pixel",    1, 1, EVAL);
X}
END_OF_lib/xlib/pixel.c
if test 1332 -ne `wc -c <lib/xlib/pixel.c`; then
    echo shar: \"lib/xlib/pixel.c\" unpacked with wrong size!
fi
# end of overwriting check
fi
echo shar: End of archive 9 \(of 14\).
cp /dev/null ark9isdone
MISSING=""
for I in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ; do
    if test ! -f ark${I}isdone ; then
    MISSING="${MISSING} ${I}"
    fi
done
if test "${MISSING}" = "" ; then
    echo You have unpacked all 14 archives.
    rm -f ark[1-9]isdone ark[1-9][0-9]isdone
else
    echo You still need to unpack the following archives:
    echo "        " ${MISSING}
fi
##  End of shell archive.
exit 0