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slides - Brown University Department of Computer Science slides - Brown University Department of Computer Science Presentation Transcript

  • The Moby Scheme Compiler for Smartphones (Is That a Parenthesis in Your Pocket? ) Danny Yoo Zhe Zhang Kathi Fisler Shriram Krishnamurthi
  •  
  • Vital Statistics
    • Middle-school, after-school programming course
    • All teaching by volunteers
    • Nearly 300 students (average age: 11y9m)
    • 24% female; 70% reporting race are minority; 70% on free or reduced-price lunch
    • Greater Boston, Bay Area, Austin, New York City
  •  
  • Bad News
    • The reason they’re smiling isn’t the parentheses
  •  
  • Program = Design + Programming System + Execution Model
  • Program Execution Model
  • Pascal
    • “ Pascal is for building pyramids—imposing, breathtaking, static structures built by armies pushing heavy blocks into place. […] In Pascal the plethora of declarable data structures induces a specialization within functions that inhibits and penalizes casual cooperation.”
    • — Alan Perlis
    • “ Pascal is part of the same machinery as hall passes, dress codes, advisors’ signatures, single-sex dorms, and so on.”
    • — Brian Harvey
  • begin … end; begin … … end; begin … … … end; begin … … end; begin … … … … … … … … … … end; begin … … … … … … … … … … … … end. begin … end; .
  • flights from PVD to CDG list of flights the third outward flight restricted list of return flights the second return flight ok must remember list of flights must remember restricted list of return flights
  • user typed ‘(’ ok user moved mouse ok user clicked mouse button ok different kinds of handlers
  • user moved right 10 yards ok user tilted phone left ok user moved left 10 yards ok loc: (10,0) loc: (0,0) loc: (10,0) loc: (10,0) loc: (0,0) loc: (10,0)
  • void void void
  • database, memory store, remote Web service
  • database, hidden fields, cont’ns
  • Why is this Bad?
    • What good are functions from
    • high-school algebra?
    • A LISP programmer knows the value of everything, […]
    • —Alan Perlis
    • You’ve disappointed Alan Perlis.
    • 2006 PISA scores: USA not in top 20 in math, science, or reading
    • “ Economic Time Bomb”
    • — June Kronholz, WSJ
  • void void void Why void ? The hostile operating system Why hostile? Because it’s neutral But neutrality  hostility Neutrals can cooperate (impartially)
  • User OS Callback “ World” “ World” “ World” “ World”
  • Current value of World New value of World Might be enriched with additional event information Phone example: World is current location Will invoke event-specific functions (define (on-move w d) (posn+ w d)) (define (on-tilt w o) w)
  • on-tick :: w  w on-move :: w  dist  w on-tilt :: w  incl  w on-key :: w  key  w on-click :: w  btn  w on-redraw :: w  scene stop-when :: w  bool
  •  
    • (define width 400)
    • (define height 300)
    • (define initial-world 0)
    • (define PLANE )
    (define (incr-time w) (add1 w)) (define (render-world w) (place-image PLANE (* w 10) (image-height PLANE) (empty-scene width height))) (big-bang width height 1/10 (on-tick incr-time) (on-redraw render-world))
  • World World Scene World World World
  • World World Scene World World Bool
  • Moby
  • What It’s Not
    • A “Scheme compiler for smartphones”
  • What It Is
    • Compiles programs written in
    • Scheme (Beginner Scheme, for now)
    • + World
    • Currently for Android, partially for J2ME
  • A Little More
    • Scheme (Beginner Scheme, for now)
    • + World
    • + GPS
    • + Tilt
    • + GUI-World
    • + Rudimentary Web Services
  • Baseline
    • All student programs will run on phone *
    • * A little legalese elided
  • Rolling Out of Time
  •  
  •  
    • (define WIDTH 300)
    • (define HEIGHT 300)
    • (define-struct vel (x y))
    • (define target (make-posn (random WIDTH) …))
    (define-struct world (posn r vel)) (define initial-w (make-world (make-posn …) 30 (make-vel 0 0))) ;; game-ends?: world -> boolean (define (game-ends? w) (or (<= (world-r w) 1) (collide? w)))
    • ;; tick: world -> world
    • (define (tick w) (make-world (posn+vel (world-posn w) (world-vel w)) (- (world-r w) 1/3) (world-vel w)))
    ;; tilt: world number number number -> world (define (tilt w azimuth pitch roll) (make-world (world-posn w) (world-r w) (make-vel roll (- pitch)))) (big-bang WIDTH HEIGHT 1/20 initial-w (on-redraw render) (on-tick tick) (on-tilt tilt) (stop-when game-ends?)) (define (tilt w azimuth pitch roll) (update-world-vel w (make-vel roll (- pitch))))
  • Minding the Store
  •  
    • (define mymaps-url &quot;http://maps.google.com/maps/ms?ie=UTF8&...&msid=...&quot;)
    • (define ALL-PLACES (parse-places (parse-xml (get-url mymaps-url))))
    • (define ALL-ITEMS …)
    (big-bang ... (on-redraw render) (on-location-change update-loc)) ;; update-loc: world number number -> world (define (update-loc w lat long) (make-loc lat long))
    • ;; render: world -> scene
    • (define (render w) ... (description w) ...)
    ;; description: world -> string (define (description w) (items->string (matching-items-nearby w))) ;; matching-items-nearby: world -> (listof item) (define (matching-items-nearby w) (places-matching-items (nearby-places ALL-PLACES w)))
  • Homeward Bound
  •  
  •  
  • The World is Not Enough
    • Parallelism/Concurrency
    • In-place updates
    • “ Safe at any speed”
    • — John Jannotti
    • Universe for distributed computing
    • Moore versus Mealy
  • On the Internet, nobody knows you’re a Scheme program JavaScript Java Processing J2ME Flash/ActionScript Objective-C NXT NXC RobotC BricxCC Design Programming system Execution model {
    • Port Moby! [email_address]
    • Teach Bootstrap! www.bootstrapworld.org
    Thanks : Danny Yoo Zhe Zhang Kathi Fisler Emmanuel Schanzer Matthias Felleisen (rest )